It's possiably stuck the pins are not releasing maybe loosen the line to relief pressure then? It must work on a relay to release itPretty sure the remote attachment lock is operated by holding the switch for it and using one of the loader controls to run the lock. Switch is on the left panel so I presume the right control lever runs to lock. Are the attachment pins free to move? Manual lock pins are rather quick to gum up.
Update there was no power to the switch. Powered it up off came the bucketIt's possiably stuck the pins are not releasing maybe loosen the line to relief pressure then? It must work on a relay to release it