A problem I've had where I tried to start and it Clicked then nothing lights (Dash) went out) Saw it on a Chevy Pick up last week too.
Now on the chevy I narrowed it down to one wire and 2 connections. with one highly suspect connection..
On the motor home I narrowed it down to that SPECIFIC connection
The positive battery terminal.
On my motor home Damon or Workhorse (not sure which) put standard ring terminals on the battery leads. NOT the lead terminal Chevy used (But the pick up proves it makes no difference) and the terminal needed cleaning.. Testing narrowed it downm, Cleaned it up and Varoomn.
Don't know how the pick up did. Suggested they try cleaning before hiking to the auto parts store across the parking lot but.. i was outta there.