Installed 82-238 mortise lock

Thanks for posting. Sorry to hear you're having trouble installing the lock. I agree, try re-installing the 82-238 first and see if that does the trick. Also, try manually throwing the lock with a slotted screwdriver. Does it budge? If so, the issue could be with how the handle set interfaces with the lock; make sure the thumb lever on the extant handle set is not damaged in an way. Let me know how you make out.