i think boost is only good one way. you maybe left something on in coach that you've heavily drained house batt. put house batt toggle to ON or USE and plug rv to shore power overnite then try.
be sure to toggle house batt to OFF or STORE when MH is not in use. otherwise, maybe like my rig and maybe yours too - there is a BIRD relay that connects house batt to chassis, and as long as chassis batt is lower than house batt, the house will drain to chassis batt. a goofy thing, i think.
the BIRD is one way like the dash boost toggle, but they are somehow different. i think the boost is for manual action in emergency. the bird allows shore power to charge both batteries, or this is what i make of the distinction, anyhow.