Died after 5 sec, cranks, won't fire

[MAX A/C]

'01.5 HO, all stock, 109K miles, newer lift pump. Bought used with 100K, so I don't know any history.

Running some erands, at my last stop the truck started as usual, but after 5 seconds it quit as if someone turned the key off. Then cranked only, no fire. AAA towed it home, and I'm trying to figure it out.

Lift pump whirs away, got fuel coming out when I loosened the VP44 inlet (schrader valve banjo). If it's supposed to spray out a lot, it didn't. Just maybe a tablespoon full with the 2-sec key on lp cycle.

Battery power good. I took off the underhood Power Dist Center cover, and it's not getting voltage to the main leads (the ones with the 140 amp alternator fuse) with the key in the on position. Is this correct?

Codes thru odometer: 1693 and 0562:Charging System Voltage Too Low Supply voltage sensed at ECM too low. (These may be left-over codes from when my batteries died, and I took them out and it sat for a week like that while I got around to replacing them.)

I disconnected batteries for 2 hours to reset anything that may need it. No luck.

This is a dedicated-camping vehicle, sits most of the time. However, I did just get back from a 4,000 mile trip--it ran flawlessly. I'm sure glad it started fine when I was in BFE Death Valley!

Help. Any suggestions?
Scott