The Proof of Keys event has been established in order to make every cryptoexchange prove their BTC solvency. Every customer is emboldened to withdraw all BTC holdings to private keys controlled by them personally. Nevertheless, per Trace Mayer and the official webpage of the said event, apart from earlier mentioned HitBTC, some cryptoexchanges had also encountered problems before or on the day of the event.
Not all of the cryptoexchanges enlisted in the section of event failures were experiencing troubles with BTC withdrawals. Coinbase stated that the trouble that was reported at the end of last year was fixed subsequent to its original report.
Bitfinex resumed its operations approximately 60 minutes after the power outages it reported in the morning.
HitBTC did not provide any comments regarding its ongoing troubles with funds withdrawal. There are even speculations that the cryptoexchange might actually suffer from solvency problems.
Purse.io, which technical is not a cryptoexchange, but rather a service that facilitates acquisition and utilization of BTC using Amazon Prime, did not provide any response to its withdrawal troubles encountered by some of the customers.