Ok, I had a look at the logs, and noticed this
[2024.07.31-00.37.55:422][350]LogOnlineSession: STEAM: Found 50 lobbies, finalizing the search
So my suspicion is that perhaps because I’m using a steam app id of 480 (Spacewar) and many others are as well, my lobby finder is hitting the cap before it can find my session that I created.
So I guess the next step is to try and use C++ instead in order to limit the lobbies to the same type somehow, because BP seems too limited in order to do this unless you use Advanced Sessions plugin.