Some things to try.;
Restart the iPad by holding down on the Sleep button until the red slider appears and then slide to shut Off. To power up hold the Sleep button until the Apple logo appears and let go of the button.
Reset the iPad by holding down on the Sleep and Home buttons at the same time (for about 10-15 seconds) until the Apple logo appears (ignore the red slider), then let go of the buttons.
Look at iOS Troubleshooting Wi-Fi networks and connections http://support.apple.com/kb/TS1398
On your iPad go to Settings > General > Reset > Reset network settings and see if that enables you to connect.
If none of the above suggestions work, look at this link.
iPad Wi-Fi Problems: Comprehensive List of Fixes