For the physical SIM I suggest first to check for successful IMS registration like this Wifi calling not working, e OS 3.5 on FP6 - #3 by tcecyk
If this shows correct then I would phone the carrier and ask for a Network reset. This may or may not be the same as APN reset.
MVNO is set to IMSI instead of None
I don’t know the full significance of this but it seems MVNO are a little more prone to difficulties with ~early 2026 changes to the APN “system” in AOSP. Loosely speaking IMSI would seem an improvement on None.
If you phoned the carrier you might ask if that is a recent change.