Certainly check the breaker, but the 3.07v at the batteries is Certainly sounding like dead house batteries... too dead to activate the use/store solenoid... the 13.46 at the monitor is from the converter when plugged in to shore power.
Best bet would be to check water in batteries, and use an external car battery charger to see if they come back. Iím thinking with good voltage on batteries, things will work as they should.
Batteries can easily drain in a couple of days depending on what is on... an interior or basement light... smoke, CO, and propane detectors, etc...
Now the stereo should be working on the converter... but the genny may be only seeing the 3.07v from batteries assuming (dangerous thing) it isnít wired thru the use/store switch.
Not yet retired...
Florida (Michigan transplant)
2014 Hurricane 32A
2000 Infinity (previous)