3336 is ALIVE for me right now..
well, then I have absolutely no idea what's going on here...
I have also tried to remove the pool and re-add it but it didn't help
If it's alive for me and dead for you, either nicehash banned all and whitelisted me or it banned you or you have connection issues to nicehash.
In either way nothing to be done.. maybe ask nicehash?
Ah, maybe you specified incorrect BTC address? It does go DEAD if it is not valid.