For your slide out hydraulic system look under the inside step. The lid raises up.
Also look at page 171 in your owner's manual. It has a nice diagram of the slide out hydraulic pump and reservoir.
It says: Access the slide room hydraulic pump in generator compartment (curbside) at front of the motorhome
behind the firewall.
Regardless, you really need to check your chassis battery voltage level unplugged without the charger running. I suspect you have low CHASSIS batteries.
Then check the Intellitec Big Boy solenoid back in the engine compartment. It's under the plexiglass cover to the right of the engine. The Big Boy combines the house and chassis batteries after the house batteries reach a preset voltage (assuming your Inverter is set up for charging correctly). This charges the chassis battery.
The problem is the copper contacts inside the Big Boy get carbon build up and do not make contact. As a result, many of our chassis batteries get low.