Help phone does not recognize t-mobile sim

[joelpps]

I had my Atrix unlocked from ATT&T about a year ago to use sims whin I travel to foreign countries. It had no problem recognizing them and being able to use the phone. However I just got a t-mobile sim and it does not not ask me for the subsidy unlock but it never gives me service.

I have and unlocked chinese phone and the sim works fine so it appears that the sim in not defective.

Any ideas ?