From your description of the black collar, I'm assuming you have an '02 or later Cruiser which has different connectors from the '01. That collar is actually a locking ring. Try pulling it back, inserting the plug as far as possible into the radio, and then releasing the locking ring.
When the new connector first came out, Chrysler had to issue a special bulletin to warn their mechanics not to damage the connection by forcing the plug out without pulling back on the locking ring.
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