I would bet first your battery is discharged, but an original univolt that old should not be trusted.
I would check the voltage, then plug in to shore power, and check the voltage again. That will be quick checks of the battery and the univolt.
"The further a society drifts from the truth, the more it will hate those that speak it." George Orwell
'08 34' SO, '12 Ram 2500 4X4, Big 6 cylinder sludge burner.