Cellular Settings screen is blank, can't turn on Cellular Data
When I go to Settings > Cellular, the screen is completely blank - I mean nothing. Similarly on the Control Centre panel, Cellular Data is grayed out. I've done the usual: multiple restarts, Reset Network settings, tested the SIM in another phone (works), and tested another SIM in my phone (doesn't work). I'm in range of the Carrier. This started as I was switching SIMs between phones. Running iOS 13.3.1. I am out of ideas. These are coronavirus days, I am locked up after travel and the Apple stores are closed. Does anyone know what's going on?
iPhone 8 Plus