Distant Horizons won't let me join my own server

For some reason trying to install the mod on my own client makes the server show this. If I remove the mod it lets me join the server. I don't know what I did wrong. I know that the mod can't be put in the server because of the factor it will crash it. Tried fiinding answers online but nothing came up. So now I'm here. If anyone can help me that would be greatly apricated.