No SIM detected all of a sudden
I've tried the basic troubleshooting for this; this SIM works fine in other phones. Cleaning the SIM had no effect. Phone hard reset, no effect. Shimming the SIM card, no effect. Nothing out of the ordinary has happened to this phone; it was left on a countertop working fine after having just made a phone call, then a few hours later, it reports that there's no SIM installed.
Also tried other SIMs - no SIM is recognized in this phone. Network options also reset to no effect.