First, you need to post year, make and model of RV you're asking about, since you don't have it listed in your profile.
Second, if you're talking about the battery monitor panel, you need to test with a hydrometer or multimeter. Since your'e plugged into shore power, the panel will always show full charge. You need to unplug from power and then test the battery after an hour.
Third, slideouts almost always have their own separate 30 amp fuse. My Rockwood had it underneath, along the trailer frame, next to the slideout.
Fourth, depending on the slideout, it should have a manual way of getting the slideouts in.
Dan-Retired California Firefighter/EMT
and Zoe the Wonder Dog(R.I.P.)
2016 PrimeTime TracerAIR 255, pushing a 2014 Ford F150 SCREW XTR 4x4 3.5 Ecoboost w/Max Tow Package