There are a few known issues with server installs potentially conflicting.

If you are joining the Occupation server but are getting kicked to main menu after joining the server, check to see if you have the separate Squad Ops Maps Mod installed. If you do have the Ops Maps Mod installed, uninstall it (you can try just reinstalling it, but this seems to be a temporary fix).

If you are trying to join the Mixed Modes server and are getting disconnected, ensure that you have the latest versions of both the HC mod and Maps Mod.