i am also using 2 sp80s and could not get my base to show online ever.
Welcome to our forum!
From the investigation of @thomasrope’s case Connecting SP80 Rover to NTRIP Caster, I can tell that everything appeared to be working well from Caster’s side. However, the SP80 base sends corrections in a format that the SP80 rover cannot process.
We cannot recommend something particular here as these receivers are not our products.
You can share your credentials for Emlid Caster to email@example.com so that we can check the state of your mount points and ensure that everything is set correctly there.