Help: Cant connect to this server.

So I've been playing on this server for a few days and when I tried to connect today, I got some weird error message. It says "Ip forwarding is enabled but spoofed data can't be decoded or is missing".

I tried connecting to other severs and I can. I also tried on another computer and I got the same message. Ive tried running different versions and it still wont work. Other people seem to have no problem connecting.

Please let me know if I'm missing something or if theres a way to fix this. Thanks.