Originally Posted by Guigsy82
...... We have since attempted to recharge the AGM batteries overnight from 15amp source with both batteries showing as fully charged but only reading 9V on the monitor. .......
Which monitor showed them "fully charged"?
Which monitor showed them at 9V?
Obviously there is an issue there. If one part of the system has voltage and the other part does not, that could be a problem with the use/store relay or it could be a DC fuse / wire issue.
As mentioned above, get a multimeter. Watch a couple of YouTube videos on RV electrical systems. Understand what the converter / battery / fuses do. Get a good idea of what you will be looking at. Then go to the Airstream web site and get a copy of the manual. There is an electrical schematic in there.
From all that, you should be able to trace out the voltage from the converter as it heads towards the batteries. At some point things are going to look weird. That' likely the point your problem is at.
If none of this makes any sense, call an RV tech and let them trace it out. Far better to pay somebody than to mess things up making bad decisions.