assume you checked but if not
Just a long shot. not being there
putting clamps from charger on battery squeezes
them ( postive & negative terminals show battery good .
But if cable loose not real tight on each + and -
Making good connection
Power may not be getting to starter.
Just give them a good shake to make sure.
cost nothing :wink:
PS: YOU also just did some New wiring
might have a look there too
wayne