Customers of mobile-only banking start-up Revolut had a tough time accessing the app Thursday.
The financial technology firm lets people spend and transfer money internationally without fees. But when it decided to allow users to buy, hold and exchange cryptocurrencies including , and Litecoin, some ran into difficulty.
Revolut introduced a temporary queuing system to gradually open the feature up to its users. Those who had paid for a premium version of the app were given immediate access, while standard customers had to either ask others to join or upgrade their account to access it.
As it rolled out cryptocurrency support, some were unable to access the app or use certain features, Revolut said on Twitter on Thursday, adding that it was "blown away by the number of people signing up."
The company said it had "resolved the issue" by Thursday evening.
Revolut operates its digital currency support feature via the Bitstamp exchange, a venue that hosts the largest volume of transactions across the European Union.
An increasing number of investors have shown an interest in bitcoin, as derivatives exchanges CBOE and CME both gear up to launch bitcoin futures contracts.
On Thursday, its price surged dramatically, hitting a fresh record high, but the price of the cryptocurrency diverged among various exchanges. While Coinbase put the figure above $19,000, Bitstamp's figure was seen below $16,000. Prices pulled back to $14,095.62 Friday morning, according to Coindesk data.
"Essentially, due to the overwhelming demand, we had some temporary technical issues as we upscaled our systems to cope with demand," Chad West, head of global brand and communications at Revolut, told CNBC.
"We implemented a queue (feature unlock) to help gradually onboard customers, but the response to either upgrade to Premium or refer 3 friends proved very popular. We're back up and running again."
The company stressed that the issue was only affecting certain customers.
Revolut applied for a European banking license last month, to enable it to provide other financial products like credit and deposit services. It has signed on more than 1 million users, a figure that eclipses competitor digital challenger banks like Britain's Monzo and Germany's N26.
Revolut's CEO is a supporter of digital currencies and last month told CNBC they were "definitely not a fraud," contrary to the views of a number of executives from big banks on the subject.
Jack Dorsey's Square has also been testing a bitcoin function on its Cash app where users can buy and sell the cryptocurrency. It said earlier this week that it would expand this feature to more of its "most active" users.