SIM not provisioned on iPad WiFi + 3G

I have tried a microsim in my new iPad WiFi + 3G 64gb, but I can't access AT&T network.In the general network settings, a message "SIM not provisioned" appears on the iPad. Then it says 'Waiting For Activation � This May Take Some Time'.SIM activation is handled solely by Apple's own servers. Your iPad activation request is in the queue. You need to wait it out.