I've been having this issue with my sim card since right after I flashed the latest CM 11 nightly (coming from a previous version). I just updated my bootloader and switched from TWRP to CWM earlier today. I had flashed the new nightly and after it asked for the system language, I received a pop-up window telling me to review my sim card instructions. This hasn't happened to me before, so I am extremely nervous and have been searching the web/forums for the entire afternoon with no such luck at finding a solution. I finally decided to make an account and post this thread with hopes that someone will be able to solve (or at least point me in the right direction to solving) my sim card error. Sorry if the answer is very obvious and I had missed it or something, I'm in a state of panic to be honest
Any help is greatly appreciated.
EDIT: I found a few links to a site for unlocking the network, but is this what I am looking for? I want to be 100% sure before I do anything risky. (I can't post the link because I am a new user :/ )