Payment systems giant Visa recovered on Saturday from a hardware issue that had left it struggling to process transactions at bars, shops and cash machines across Europe.
The blockage left some customers stuck at the tills in stores across the continent late Friday, whilst others were forced to queue at automated teller machines (ATMs).
"Visa has resolved a technical issue which occurred yesterday in Europe and prevented some consumers from using Visa for payments," the firm said in a statement at 04:32am (0332GMT), more than 12 hours after it first reported issues.
"Visa Europe's payment system is now operating at full capacity, and Visa account holders can now use Visa for any of their purchases and at ATMs, as they normally would."
The firm said the issue was a result of a hardware failure and "is not associated with any unauthorised access or cyberattack", whilst chief executive Al Kelly apologised to customers and businesses "for any inconvenience".
"Our goal is to ensure all Visa payments work reliably 24 hours a day, 365 days a year. We fell well short of this goal today," he admitted.
A Visa spokesman told AFP on Friday evening -- as the problems unfolded -- that it was not possible to say how many users across Europe had been affected.
However, a 2017 report by the UK Cards Association reported that Visa debit cards account for 97 percent of all debit cards, meaning the disruption is likely to have had a large financial impact.
On Saturday, the Daily Telegraph also reported that more than £1 in every £3 in the UK is spent on a Visa card, using a system designed to process up to 65,000 transactions per second.
Visa users took to social media to complain and banks tried to explain the situation their customers on Friday -- however the disruption seemed to vary on a case-by-case basis.
The Royal Bank of Scotland's Twitter help account said cash machine withdrawals were unaffected, whilst Paymentsense -- which provides card machines, online payment gateways and virtual terminals to some 60,000 independent businesses in Britain and Ireland -- advised users to try paying via contactless transactions.
After the hardware issue was resolved, Paymentsense said customers continued to experience "intermittency" because of a backlog in transactions.
In Spain, the Guardia Civil assured customers on Twitter, saying: "If you cannot pay, you have not suffered any theft or hacking."
Russia was spared the chaos as it has its own National Payment Card System (NPCS) to prevent western sanctions creating a financial crisis.
"In Russia, all card payment transactions are proceeding normally and no problems are being observed," TASS news agency quoted a spokesman for the NPCS as saying late on Friday.
France was also exempt from the issues, according to the French Association of Bank Users (AFUB).
"The explanation is probably related to the fact that in most European countries merchants are in direct contact with Visa when paying, while in France the payment passes through an intermediary," secretary general Serge Maitre told AFP.
"It's a sort of airlock."
In London, pub the St James of Bermondsey was almost empty on what should have been a busy Friday night -- with a "cash only" sign on the bar seemingly deterring customers.
Business seemed to pick up only later in the night, as card transactions began to go through without issue.
In a Primark store on Berlin's Alexanderplatz, frustrated customers were queueing for 20 minutes to pay on Friday. Staff did not know why transactions were not going through.
However, in the neighbouring store, transactions were being processed without any problems.
Sandra Foy, who owns a bookshop in Manchester, northwest England, told Sky News television: "I run a small business and the loss of any business is a big deal for us."
The BBC posted a picture of a London supermarket worker standing outside holding a sign reading: "cash only".
It cited Elle Gibbs-Murray, from Bridgend in south Wales, as saying she was stuck in traffic on the Severn Bridge between England and Wales for 45 minutes as drivers were unable to pay the toll by card on Friday.
Alex Neill, Which? consumer magazine's managing director of home products and services, said: "Visa and the banks need to ensure no-one is left out of pocket due to this outage."
"We strongly advise people to keep any evidence of extra expenses they've incurred in order to claim them back."