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You need to remove the radio and sit it in the seat unplugged for 4 plus hours so it can discharge and reset. If the radio then still fails to recognize the cartridge correct allowing you to eject the CDs then it will need to be replaced. You can attempt to take the face plate off and try to unjam it, however there are no manuals to do this offered to auto techs from the audio manufacturer.
Auto Zone sells these special tools for 8$ which will allow you to pull the radio out.
Once you have done step 2 and 3 then pry off the trim cover gently using a tool like a dull kitchen knife.