PSOBB has trouble with WiFi on all servers from my experience. I had the same issue for a long time until I changed my WiFi. It wasn’t even necessarily slow, just didn’t want to connect. Also if there were more than 2 people in the group I would freeze entering the game. My nickname was DC.
Hotspot your phone, if it logs in no prob then it’s the WiFi.
Or hardwire to your router.