Just wanted to share this response from 24hbet support:

"Please be advised that your recent requested withdrawal of xxx EUR, failed due to an unknown reason.

Please proceed to try your deposit attempt once more in this case."

Withdrawal failed, but they had no trouble back in the day I was making a deposit. I am very interested to see how they will explain this "unknown reason"...

:facepalm: :facepalm: :facepalm: