Mordok

I just recommend opening the entire range, 16000 - 17000, rather than fuss with individual ports. You don't really need enough slots for 400 players, but it keeps things simple.

You try to open only default port for server "16261". Server need first 16261 +1 for every player. For example local/external start 16261 - 16291 (+30 players).
I have got errors from provider few days ago. I have opened ports and nothing happens. The problem was, that i had IPv6 and portforwarding works only with IPv4.