Underneath passenger side, about midway between front and rear tires.
The fluid would be first thing to check as sometimes the system needs fluid to both go up as well as go down!
I suggest checking the manual for the jacks to be certain where the correct plug is located as well as how to verify the level is correct.
Reason for care is that there are some which have an easy to spot plug on the side of the tank. That one is too low and when you pull it out, fluid can run out all over!
On my first go, I pulled the wrong one as the correct one was on top!
If not a fluid problem, there are solenoids which may need checked/ corrected. A solenoid is just an electrically controlled valve that opens/closes much like a faucet does water.
If one or more of those solenoids are clogged or not opening correctly, the fluid doesn't move when and where it should.
Definitely read the warnings before opening any of the lines as the high pressure can be very dangerous if we do it wrong!
Checking the fluid level is safe but opening the lines can be BAD!
Why no RV year, make and floorplan on MY signature as we suggest for others?
I currently DO NOT have one!