Uh oh...voltage crash and now won't turn over

Will try all the above.
I have the 2 wire connector and post alternator. Green and blue from the vr to the contacts. Alt housing is also grounded to the block. Never had an issue. My next thoughts were trailbeasts in that order but i'll def make sure of the battery condition prior. Working today and tomorrow so tomorrow night or Tuesday will be the soonest I can get to it. Will put the charger on it tonight.