Neither my door or ignition key will fully insert into my tailgate lock.

Do I have bad lock or does the tailgate use a different key?

 

Door key should work in it.

 

Try squirting some WD40 or similar in the key hole.

Either the lock tumblers are corroded seized, the lock is bad or the PO replaced it.

 

My XJ has a story to tell, because the ignition, glove box, and hatch share a key (which I have), the passenger door uses another key (which I have), and the driver side door uses a third key (which I do not have)