If you look under the front passenger side tire, the UHG will be there if you have one. It hangs under the engine... and you must take care not to hit it on curbs when you park. As the others said, if you don't have it, you can't run the rear AC while driving ... only when plugged in.
Did you buy from an individual or a dealer? Did you run the AC on your walk through?
If you plan much boondocking with this rig, you will want to add a second battery and solar.
2019 Roadtrek Simplicity SRT (almost a Zion)
2015 Roadtrek 170
2011 LTV Libero
2004 GWV Classic Supreme