I have seen many posts about the sim card error, and have now experienced it myself. I have a USC XT1768 (on AT&T), running RR for about the last 4 months. Everything has worked perfectly until 3 nights ago when, suddenly, for no reason I had no service & saw there was "no sim" recognized. A Google search led me to switch to 3G and turn on airplane mode and reboot. After rebooting, I turned off airplane mode and service was restored. However, I am forced to use only 3G. After multiple "tests" switching back to 4G LTE, I always lose service. Yesterday, I "tested" again and LTE worked for about 8 hours before I got the sim card error. I re-did the airplane mode/3G process and I was back in business...just with 3G.
Last night when I got the "No Sim" error, I noticed that the preferred network in *#*#4636#*#* was "Unknown". It had been set to LTE/UMTS/Auto. It doesn't seem to make a difference if I switch it to Global, or anything else. The problem remains. Oddly, when I just entered *#*#4636#*#*, the preferred network setting was on WCDMA. Weird...I didn't select that setting.
Anyway, maybe this can kind of help someone else.