Most likely a problem with Xsolla. I used Xsolla a few weeks back to pay for my ESEA Main fees and ESEA Premium subscription with Bitcoin (they used Bitpay as a payment processor) and things went just fine, guessing Xsolla removed Bitcoin as a payment method recently. Haven't been able to find anything on their site about this unfortunately. Xsolla's main site is here (
click for link), contacting their support might help shine a light on why BTC's not available as a payment method right now. There aren't any third-party services that I know of to buy Faceit subs AFAIK, best alternative for now is a crypto-to-fiat conversion 'till Xsolla adds BTC as a payment method again.