iOS 6 activation error on iPhone 3GS without SIM card

Solution 1:

The message you describe is what happens when a locked phone is restored by iTunes without a SIM present from the carrier that the phone should be locked.

You could use any of the IME I look up tools on the Internet- some are free and some are paid and all make me worry they are harvesting databases of IMEI/serial number/other data in exchange for providing you a service by looking up your phone in the carrier database.

Of course, you can always contact the carrier in question to see what is needed to get service or a Sim card for that device.

Solution 2:

I had a similar error once, and if I remember correctly, it was that the time on the iPhone was wrong (months or years, I think). Setting the time correctly allowed it to go through.