Q: no sim card installed ipad 3rd generation. not connecting to server once i put the sim card back into ipad. ipad is connected to wifi. need help

I took my sim card out of my ipad. The sim is not activated. I kept getting the message "no sim card installed" every 1-2 minutes popping up. So I put the same sim back into my Ipad. Now it takes me to the choose a wifi network screen. I have my wifi connected. The next screen appears with " it may take a few minutes to activate your Ipad". It never activates. It gives me the 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 in a couple of minutes.  If this problem persists, contact apple support at apple.com/support. Please help.