If you can exit the app:

1. Exit the GTPKiosk App (instructions here)
2. Verify that the iPad is connected to Wifi.
3. Re-run the GTPKiosk App.  If is is connected to Wifi and still not connecting, you may need to contact GTP Corporation to re-authorize your iPad.

If the iPad is completely "Frozen"

1. Remove the iPad from the stand
2. Press and hold the Power and Home buttons together for at least 10 seconds until the iPad restarts.
3. Replace iPad in the stand
4. Run the GTPKiosk App (instructions here)