Well, I'm no expert, but....if it were me, I would start to look for possibilities to eliminate.
Sounds like you are getting no power or insufficient electrical power anywhere. Is that correct?
Then the first thing I would do is swap out for a known good battery or a jump pack. Batteries can test as good even if defective (this recently happened to me with a very new battery). A simple and cheap thing to check first.
Good luck!