^+1 with Doug! Very common for door locks to seize up due to lack of use. Everyone always uses their fob, power lock/unlock buttons or external keypad instead of the 'ol key-in-the-door-hatch-trunk method. Fwiw, I've had locksmiths tell me to shy away from graphite, liquid or powder, to free up locks. They claim it'll eventually gunk them up and make matters worse. Wd-40 is their go-to for cleaning/unbinding locks.