Q: My IPAD 2 display No SIM error message despite having inserted a workable sim card

Hey rahmaniyeit,

Although the following is for an iPhone, most of the steps should still apply to your iPad. try them out and see if that resolves the issue:

1. Update your iPhone to the latest version of iOS.
2. Toggle Airplane mode On and Off.
3. Try turning iPhone off and then on again.
4. Check for a carrier settings update. Tap Settings > General > About. If an update is available, a prompt will appear.
5. Remove the SIM Card and verify that it is a valid, carrier-manufactured SIM. Also verify that it is not damaged, worn, or modified. Then reinsert it.
6. Restore the iPhone.

If you still are unable to resolve this issue, contact Apple support for further assistance.

via: iPhone: Troubleshooting No SIM

http://support.apple.com/kb/TS4148

Have a great day,

Delgadoh