Note II - LTE suddenly asks for Sim Network Unlock PIN

I have this phone GT-N7105 which I received from France as a gift from my brother. When I got it one and half years ago, it had its original network customized (Orange) stock OS. However, about 6 months later, I installed the latest (4.2.2 kitkat) version from sammobile and upgraded the OS. It was working fine as well. About 2-3 weeks back, I installed CM12-nightly lollipop custom rom on it and it was still performing well. After installing one of the updates from CM12-nightly a week ago, the phone suddenly displayed the message "SIM/RUIM Perso Locked- Emergency Calls Only". And once you reboot the phone, it asks for Sim Network Unlock Pin code. I reflashed the phone with original 4.4.2, then reflashed the modem, but still no luck. Any tips or suggestions?