Disruptions began on Sunday morning with "almost all" routes cancelled or delayed until further notice, CrossCountry said.
The power cut at CrossCountry's control centre in central Birmingham meant the systems used to manage the network were offline.
The "significant and unforeseen disruption" affects major routes including between Birmingham and Manchester, Glasgow and Edinburgh and York and Newcastle.
CrossCountry has since posted on X: "A full CrossCountry service is expected to operate on Monday 24 August following a power cut affecting our control centre today, Sunday 23 August. Passengers are still advised to check before travelling tomorrow."
The outage coincided with several football matches on Sunday, with National Rail warning that other services to Manchester, Liverpool and Newcastle would be "extremely busy" as a result of the cancellations.
Services between Peterborough, Cambridge and Stansted Airport continue to operate at almost normal levels because of planned engineering work.
A CrossCountry spokesperson previously said: "Although colleagues are working hard to safely operate services using alternative processes, CrossCountry services will be significantly disrupted on Sunday 23 August.
"While we will run as many trains as possible, passengers should expect significant reductions to services and cancellations across almost all CrossCountry routes throughout the day.
"We are sorry to passengers affected by this significant and unforeseen disruption."
It's at the control centre that CrossCountry monitors the locations of trains and oversees staff changeovers.
Some passengers took to social media to voice their frustration at the disruptions.
One commuter said in a post on X that their train from York to Birmingham had been cancelled, and they were the only person in their business with a key.
Another passenger demanded a refund and wrote: "Is there any responsibility towards passengers?"
CrossCountry was found to be Britain's worst-performing train operator in a Transport Focus survey of passengers.
Other train operators continue to run services on the same routes.
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A rail replacement bus service had already been planned between Leicester and Peterborough, and its operations have been unaffected.
CrossCountry specialises in long-distance travel, with some of the routes cancelled on Sunday including Edinburgh to Plymouth, Penzance to Leeds and Nottingham to Cardiff Central.
The CrossCountry spokesperson earlier added: "Ticket acceptance is in place with other train operators, and customers will be entitled to Delay Repay compensation. Customers who choose not to travel can claim a refund from their original point of purchase.
"We are working closely with relevant partners and will provide further updates as soon as possible."
Denmark, Iceland, Faroe Islands, Finland, Norway and Sweden said they had "serious concerns" about the "governance and high-level decision-making" of FIFA in a statement released on Sunday.
Most Nordic nations had already suggested they would not support Mr Infantino's re-election at the FIFA Congress in March.
Norway FA president Lise Klaveness accused Mr Infantino of "management by fear" last week after Kevin Lamour was removed as FIFA's chief operating officer.
The latest joint statement read: "The six Nordic football associations have lost confidence in the FIFA president and have serious concerns about the governance and high-level decision-making of the organisation.
"The Nordic football associations stand firmly with UEFA and the measures suggested by its National Associations in unison. We expect that FIFA provides binding assurances that FIFA will never again open its governance or competitions to private ownership.
"We also support the demand put forward by AFC, CONCACAF and UEFA, for a fully third-party review of the events surrounding the FIFA Forward Enterprise proposal."
CONCACAF's leadership earlier wrote to Mr Infantino and asked him to stay away from a FIFA youth tournament currently taking place in the Dominican Republic, saying his presence would "undermine" the children's matches.
The confederation's president Victor Montagliani today told Sky's US correspondent James Matthews that he just wanted people "to focus on the football".
Asked directly if Mr Infantino should resign, Mr Montagliani responded: "That's his decision. It's not my decision, those are individual decisions."
He added: "We have to follow proper governance processes and I have to respect my colleagues with that. Once we follow that, those decisions can be made by individuals."
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Mr Infantino defended his position during a visit to the Dominican Republic, where he met Caribbean Football Union members at the international under-14 event organised by FIFA Forward.
He said: "We have transformed FIFA, made it to what it is, and I stress again today to the CFU members, we are here with one job - to grow football in every corner of the world.
"We need to narrow this gap between the big, big countries and all the others. We need to give a chance to all the others.
"It's important to engage, to have a dialogue, to express views and opinions. A lot has been happening in the last few weeks and it's important that you listen, and you're able to express what your feelings are."
UEFA and CONMEBOL have both called for Mr Infantino to step down, but he appears to have majority support in Africa and South America.
The Oceania Football Confederation has also declared its support for him, though New Zealand has withdrawn its endorsement.
Various iconic landmarks from Australia's biggest city are engraved onto the medals alongside Bayern Munich's Allianz Arena, which is located over 10,000 miles away, rather than Sydney's Allianz Stadium.
The event's organisers acknowledged the "unfortunate error" in a post on Instagram, but joked: "We're not going to run from it."
TCS Sydney Marathon championed the record participation and fundraising but said: "A little too much international flavour has found its way onto the back of the finisher's medal".
The post confirmed that: "With the event a week away, this is the medal our finishers will receive.
"It's a beautiful medal, and now a little more unique. What it represents does not change.
"We're grateful to our participants and partners for taking it in such good humour, and our focus now is where it should be, on delivering a safe, spectacular and unforgettable weekend."
The post is rounded off with the caption: "You noticed. We noticed. We're human. See you in Sydney."
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It is not the first time a medal mix-up has made headlines.
Last year, the organisers of the Great North Run, from Newcastle to South Shields, had to issue an apology after participants spotted a glaring error on their medals.
The 2025 medal featured a map of Sunderland and the River Wear - and not Tyneside.
Heavy rains triggered the collapse around 2am local time in the Dar-es-Salam area of Guinea's capital Conakry.
The landslide buried nearby shacks and destroyed several homes at the open-air waste dump, with 22 people also injured - six of them seriously.
A search and rescue operation is currently under way to locate any other survivors.
One woman, Cire Diallo, lost her five children in the landslide.
She told local reporters: "I have lost all my children. All I can do is put my trust in God."
The waste dump was designated for closure on Sunday because of the danger it posed, especially during the rainy season, with the waste set to be relocated outside the capital.
Locals living around the site were given eviction notices and many were forced to vacate the area.
Dienabou Toure, minister of territorial administration and decentralisation, said: "We will ensure that the remaining families are relocated elsewhere."
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Guinea holds the world's largest reserves of bauxite - a rock which serves as the biggest source of aluminium - and the richest iron ore deposit.
However, poverty is widespread across the West African country along with poor infrastructure.
Around 3.7 million of its 15.1 million population live on less than $4.20 (£3.08) a day, according to a report by the World Bank.
Jane Coates, who says that she has felt "incredibly alone" and "deserted by the British authorities" throughout her campaign for justice for Lucy Harrison, is preparing to travel to the US.
Speaking more than 19 months on from Ms Harrison's death, Ms Coates said she hopes to meet the district attorney. She also urged the UK government to offer its full backing.
Ms Harrison, a fashion buyer from Warrington, Cheshire, was shot through the chest by her father, Kris Harrison, at his home in Prosper, Texas, on 10 January 2025, the day before she was due to fly back to the UK.
A grand jury in Collin County later decided there was insufficient evidence to bring criminal charges after Mr Harrison claimed the handgun discharged accidentally while he was showing it to his daughter.
In February this year, a coroner in England concluded Ms Harrison had been unlawfully killed, finding that her father's actions amounted to gross negligence manslaughter under UK law.
Ms Coates has now sought the assistance of Radd Seiger, who previously advised Harry Dunn's family in their campaign for justice after the 19-year-old was killed by a US citizen in a road crash in Northamptonshire.
Commenting on why she has felt "alone" during her search for justice, Ms Coates, 49, said: "I think it's not being heard - just raising all of our concerns and nothing being acted upon, and feeling like we've just been deserted by the British authorities.
"I think, save Sarah Hall, my MP, who has done everything in her capacity to raise and escalate Lucy's case, it's just felt like there's been doors shut at every single opportunity, and people haven't been there for us."
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Ms Coates, who works as a deputy head teacher, said she had expected the unlawful killing conclusion to become a turning point in her campaign.
She said she is now planning to travel to Texas with Mr Seiger in the hope of persuading the Collin County District Attorney's Office to reconsider the case after the coroner's findings. Mr Seiger said the family wanted the case lifted beyond routine consular handling.
Ms Coates said: "Although I know that it's a completely different jurisdiction, a completely different law, so it's about appealing to them in terms of our real concerns with the US investigation, with the Texas investigation, and that they do agree to reopen Lucy's case and give it new consideration."
A senior coroner ruled in February that Mr Harrison's conduct had been "reckless".
The inquest heard he had been drinking wine before removing a loaded Glock pistol from his bedside cabinet.
The coroner concluded the gun could only have been discharged after it was pointed at Lucy, and the trigger pulled, and heard officers in Texas did not carry out an alcohol test despite smelling alcohol on his breath.
Ms Coates said she was not asking the Foreign Office to interfere in the US justice system, but wanted ministers to publicly support her family.
The family have requested a meeting with Foreign Secretary Ed Miliband and other senior officials.
A Foreign, Commonwealth and Development Office spokeswoman said: "Our thoughts remain with Jane and her family for the tragic loss they have suffered.
"We were in contact with the family and provided consular support.
"We will always look to learn lessons to improve the consular support we offer to other families in the future."
It is understood Foreign Office officials are reviewing recent correspondence from Ms Harrison's family and intend to respond.
The Collin County District Attorney's Office has been approached for comment.