Yesterday my S5 just decided it didn't want to connect to the VZW network anymore. I was running Alliance ROM at the time, but I Odin'ed back to complete stock and it is still not connecting. Wifi, bluetooth, etc. all works fine though.
I took my SIM card out and put it in my wife's S4 and it connects fine so it's not my SIM. I tried reseating my SIM about 20 times and still no love.