Connects successfully - then can't find anything

[Amorget]

Little history on this. Back in 2020 or so everything worked fine for things like Q3, Pool, and 4x4. DreamPi with a purchased modem.

Decided I wanted to get it back on-line. Only thing that had changed was I went from a wireless hotspot to T-Mobile home internet, which is basically a wireless hotspot anyway. The Dreamcast will dial in without an issue, however once on-line it cannot find any of the servers. Updated to DreamPi 1.9 to see if that helped, but same issue.

Q3 can't find any servers, even if I manually put in the IP address so it doesn't seem to a alternative DNS server issue.

I've disabled the Firewall on my ASUS wireless router but I don't have much control over the T-mobile router.

I am a bit stuck as to where to look to troubleshoot this further.