iPad 2 Activation Fails

I have an iPad2 on which I recently charged the battery. Once the charge was complete, I logged off and shut down the device. When I attempt to restart the device, it enters the "activation mode", and it fails to activate. I receive the following message: "Your iPad could not be activated because the activation server is temporarily unavailable. Try connecting your iPad to iTunes to activate it, or try again later."

The iTunes approach did not work, and the activation server is still showing as unavailable. I've also removed the sim card and tried to activate the iPad, but that approach also does not work.

Any suggestions on how to resolve this issue?

Thanks, John