The bail assembly is bound up. If you release the bail and loosen the clasp by one notch you will be able to turn the key. You may be trying to close the clamshell to the last notch, but the FatCat should only be closed to the 2nd or top notch when you have skis or snowboards loaded. Check to see that the load is secure when closed to the 2nd notch.
Still need some help? contact our support team here, or by phone at 888-925-4621 M-F from 7 to 4 PT