First off, lube. Then I press the release tab and turn the key at the same time, as far left and right as it will go. Could be your tailpiece is bent or put on wrong. Ive seen people put the tail pieces on in the lever configuration and still force it in the knob somehow.
Also try banging the knob against something or tapping the collar above the release tab with a hammer gently. Sometimes you can loosen them or pop them back into alignment.
If your feeling brave the “expert mode” would be to remove the lock assembly from the knob and get at it from the back. There is probably a YouTube video on how to do it. If there isn’t, PM me and maybe ill make one and email it to you. Then I’ll post it to YouTube and make millions of dollars. The camera loves me.