Third Party Photon Bug - Unable to join the same room sometimes?

So I followed a tutorial to make a proof of concept for networking using PUN. It worked great.

When trying to implement this into the preexisting game, it was having issues - so I decided to take the proof of concept (which still worked great) and import it into the preexisting game to troubleshoot.

To my dismay, the proof of concept stopped working (I could no longer connect to the same room) once it was imported. I have checked that the room names are the same, and have confirmed that the rooms only list one player on each client.

I have removed PUN and reinstalled, and double checked the appID in PUN settings.

The ONLY difference I can think of is that the project is using collab, where the proof of concept did not.

Does anybody have any insight into this? I am totally stumped by this - changing the project should not just make it stop working.

Also for what it is worth, there are 0 errors being thrown by PUN.