After a lot of “political” hassle, a tech discovered some settings deep in the bowels of the phone were set wrong. Correcting this fixed the problem. Sorry it took so long.
Left off, I don’t know why the settings were suddenly wrong. Software glitch I guess.
Weird. And you probably needed internet access for them to debug the problem — catch 22.
Have you considered a more permanent solution? Such as at LTE 5G modem box? You can hook up antennas to it that are mounted on your roof and probably get a better signal. And it might be more reliable than a phone.
People mount them to their RVs.
I don’t know how much it costs.