You should join the actual PW owners group on groups.io. It’s been going for 3 years and has lots of people with older models willing to help.
If the batteries might have been wired incorrectly the converter fuses will blow. Otherwise, what’s been mentioned already will be your choices. Red disconnect key needs to be in and on anytime you’re using the van and want electrical, the 80A breaker (controls alternator charging), the smaller DC breaker labelled converter has a little black button on the side to reset if you’ve not got 12V power when parked.
Make sure you always have a voltmeter in the van so you can troubleshoot electrical issues and see where you lose power.
Cheers,
BL
06 Plateau TS