are the 2 batteries totally DEAD?
by that i mean, checking the voltage on the battery posts=zero?
it is my understanding that the p'lax c/c will NOT function connected to dead batteries.
it needs something like 9-10 volts to come alive and charge/convert.
my guess is u plan to let the dealer/service tech sort out the issues after towing it there,
but just in case you might wanna sort this out...
the simplest way to do this is remove the batteries and charge them ONE TIME with some other charger.
for example take them to an auto parts store and have them do a 'rapid charge' one time.
now re install/connect and put the switch in USE position.
after reconnecting and plugging into shore/ac/120v check the p'lax for output...
it should be around 13.5v to 13.8v or up to 14.1 volts.
connected to shore power it will now take 1-2 days to fully charge the 2 batteries.
it would be wise to also check both batteries for WATER LEVEL, not assume, check it.
add distilled water as needed.
the basic trouble shooting guide for the p'lax is here...
fully discharged but otherwise NEW batteries can usually be revived.
their service life may be shortened a bit.
IF the batteries have been at ZERO volts for a long time, they may not be salvageable.
the auto parts shops can 'load test' them but that may not be needed,
get them UP to ~10 volts, reinstall, flip the switch and plug in for a few days.
the owners manuals are all online and downloadable.
the tongue jack needs a minimum of voltage too or will just burn fuses.
it is not that hard to use the hand crank and u might as well practice with it now.
plugged IN to the tow vehicle the brakes should work but the tongue jack may not.
don't try charging FROZEN batteries either.