Several rail firms reported problems with pre-paid ticket collection from machines across the country on Tuesday morning.
Greater Anglia, Thameslink, Stansted Express, Southern, Southeastern, and ScotRail all confirmed they were affected by the issue.
The Rail Delivery Group, representing train operators, said the problem had been fixed at around 10:00 GMT.
Customers were advised to use staffed ticket offices where possible.
Most rail companies said any proof of purchase, such as a ticket reference number, was being accepted instead.
One person tweeted that the button to collect pre-paid tickets was greyed out on “every machine” at London Liverpool Street on Tuesday morning.
A spokesman from the Rail Delivery Group said one of the suppliers of the ticket machines had been experiencing problems receiving information from computer servers.
He apologised for the inconvenience caused to passengers and advised those affected to speak to their train company or visit their ticket office.
He confirmed the issue had affected multiple operators but not all machines across the country.
Virgin Trains said their ticket machines had not been affected.
Earlier, one rail passenger, Matthew Farren, tweeted: “Well done @tfwrail Not only is the door to get into Newport station not working, but now the ticket machines are broken too – doesn’t inspire a great deal of confidence.”
The issue only affected the collection of pre-paid tickets, and all other ticket types could be bought from the machines.
Rail ticket machines also fell out of service last June, with on-screen messages saying there was “no online connectivity”.
The issue, which was resolved after three hours, appeared to have originated from the software and systems provided by Scheidt & Bachmann, but the German firm did not provide additional information.