There are two dump valves on the rear of your coach, it sounds like they are either plugged up so the air can't escape or they don't have power to them. The problem with air bleeding out of the system overnight is common and is caused by leaks in the air system. Do you need to contact a repair center? That depends on how handy you are and how good the repair center is. You would essentially be paying them an hourly rate to troubleshoot and fix your issue. That's an expensive proposition.
It's pretty easy to check out the dump valves. There should be two wires to your dump valves, get a DVM and check for 12 volts when someone pushes the dump button on the dash. Polarity shouldn't make any difference, one side is ground the other is 12 volts. If you have voltage then the valve is inoperative or more likely clogged up. Dirt daubbers like to make nests in them. The hardest part of this is finding the valves. Mine are easy to see at the rear of the engine as should yours since you have a side radiator too.
This is the only picture I could find of my dump valves. From this you can tell where to look. It's the blurry component in the foreground of the picture. This is the driver's side of the engine at the rear, just above the lower radiator hose.
Finding leaks is a dirty, time consuming job consisting of mostly lying on your back spraying the air suspension system with soapy water looking for leaks. You do it by airing up the system and then blocking the coach with either appropriately sized jack stands or cribbing. Then just follow the air lines and spray all the fittings and components. You'll likely find lots of small leaks. A system that deflates over 24 hours is not a real problem or safety hazard.