[AC Question]

this sim card is from an unknown source keep pop up on my Motorola droid 4 how do i stop this from happening?

[B. Diddy]

Welcome to Android Central! Where did you get the SIM from?

[JL014]

I am also having this problem! Droid 4. I'm in Australia, and got a SIM card from Vodafone. Every time I power up I'm told the phone doesn't recognize the SIM. (My phone has also gone into forceshut and reboot loops several times. I've had to factory reset once already, and am even having the problem where the phone will open in safe mode without me telling it to, and loop on and off. Not reset, just turn the screen on and off. Even after all this, the SIM is still not recognized. Is maybe the SIM causing all these problems?)

[Rukbat]

The phone not recognizing the SIM can be a) the phone is locked to a different carrier, b) the SIM is defective or c) the SIM socket (or something further into the phone circuit) is defective.

Forced shutdowns and reboot loops can be due to a bad SD card or a defect in the phone.