Can't get the BoS trainee mission to reset, even tho I have completed the mission.
Any code to fix?
Please?

Just to be clear, you've completed the quest with the squire (Leading by Example) and you want to start another?
As Captain Kells is part of several other quests as well, maybe some of those are interfering. Is it possible that you've met DiMA on Far Harbor after picking up/completing your previous Leading by Example quest? If so, Captain Kells won't issue another radiant quest for you until Search and Destroy is started (or possibly completed).