Would also interest me. May it be possible that you upgraded your Windows from 1803 or 1809 to 1909?
Since I am facing this issue since I updated my OS, and to be clear, I have not played, edited or even booted the server up in months, so it might be some other issue.
Firewall stuff ain't a hard thing for me to bend it to my will, that was never the problem in my case.
It is either the OS upgrade or the Anti-Cheat software gone haywire (service offline, completely shut down, licence with kakao off the run, or simply being not supported for black desert (certification server-sided check on their backend and missing cooperation/contract related "OK")).