oceanjive

I can't find a single thing on the internet describing what is happening. I attempt to join a lobby, it gets to "waiting for host" Red text in the bottom left says "name" uses modified data file. then it istantly, without any message why, sends me back to the server list. how do i fix this? what's the problem? i've been trying to fix this for like 4 hours. i have reinstalled the game, restarted my computer, etc etc