I have a similar issue using forge. If you have the 1.15.1 variant, it will crash out every time you try to play multiplayer. Only solution i have found is to play without forge, but that limits you to just using resource packs. This may have something to do with the server itself, though. The server i try signing into has a forge installation, so maybe it is conflicting with that? Otherwise, the only way i have gotten forge 1.15.1 to work is to sign in to single player.
Sorry, man. Perhaps a rollback to a previous edition will help get you going, but it wont have those honey blocks, if i figure correctly.
