I just bought a second hand N4 to try out Android (WP8 user here).
The guy I purchased off showed me his SIM was working in it fine but since taking it home I haven't been able to get any SIMS to work in there. I have tried quite a few, all of which work in other phones.
I've done a factory reset multiple times, rebooted the phone multiple times and even tried starting in recovery mode. Nothing I do seems to be able to get any SIMS working.
Really frustrating experience as otherwise the phone works fine on wifi. Really hope someone can help me as otherwise I just spent $180 on a dud!