I'm having the EXACT same issue,and my phone is SIM unlocked and it won't recognize any of the 3 active Sims cards I tried, 1. is mine, T mobile. 2nd is My Mother's At&t, and third my buddies boost mobile sims card from his android phone from there. None either say it's the wrong Sims card or anything just that I don't have a sims card. Oh yea and where your able to input an APN is all greyed out so I can't even try to type in an APN manually. I know the card is good. I use it on my Samsung Galaxy 2. The Mytouch 4G is my old phone. I kept it for a just in case phone. Phone is rooted and it was running CM 6.5, then I put a stock rom on it now to see if the rom was the problem.. must not be. I'm fresh out of Idea's. Anyone here got any?
▐ Phone: T-Mobile Iphone 5▐ ▐ ▐
▐ Tablet : Samusung Galaxy Tab. 2 10,1