New Batteries should fully charge on the generator after some hours as you expressed.
I would check or have someone check the charging amps, which should be displayed on the house energy management panel. On low charge on the generator, it may be drawing over 15 volts or more. 14.5 is average on our son batteries that are low. Maintaining volts should be about 13.5.
If those batteries are good having only been discharged fully one time, they will charge back up but it will take a while.
The energy management system is adjustable. Read the manual...better yet find a good RV Tech. Check to make sure your generator switch is turned on. Freightliner didn't turn ours back on three weeks ago.
I suggests find a good Tech to check charging system and batteries.
If you are near the Kingman are I suggest Trotters. I'm a little tired tonight and slow.
If you had someone change out the batteries they no doubt turned off the main switch near the door, and they may have turned off the generator. And the inverter/charger check for three little knobs like on our ,or whatever on yours and make sure they are pushed in.