Federation takes a little bit of getting used to. Based on your username, you are logged into shi.itjust.works. If you go to any community from that instance you will already be logged in. If you want to be logged in on another instance you have to visit it from your instance. https://sh.itjust.works/c/rpg@ttrpg.network you will be logged in. https://ttrpg.network/c/rpg you will not be.

Try searching with the full url https://ttrpg.network/c/rpg. That’s worked for me once when !community@instance didn’t.