How long had it been sitting before you got back to it. The inverter draws power all the time unless it has a HARD on/off switch like the Prosine line does (not many do) and several other devices on the RV are full powered even when "Disconnected" Propane detectors and such are the most common.
If it's been sitting long enough the batteries run down.
7 hyears for AGM's... Low end of "Anticipated life" 10 is about the high end but you might have 'em tested.... My Flooded wet cells (GC-2) lasted 9 years. My AGM's only about 5 Reason number 2 why I'm not a fan of AGM's. Rea$on Number 1 you can likely gue$$ from thi$ po$t.