It could be one of two things..... a leak or a bad pressure sensor.
I had this happen on my last coach, a 2018 Outlaw 29H. Even though the jacks were retracted the alarm would sound once I released the parking break. The motor would even run until it tripped the 100A breaker and then the alarm would quit. After doing extensive troubleshooting I determined it was the pressure sensor. If the sensor does not detect at least 2250PSI, it assumes the jacks have not been retracted and sounds the alarm if you release the parking break. I ordered a sensor on Amazon and it fixed the problem. It was still under warranty and Thor reimbursed me for the part.
I also had this happen on my 2020 Magnitude. I had a very small leak at the power unit and was waiting for my dealer to fix it. While I was waiting for my appointment the leak got worse. On the way home from a trip the alarm went off. This time it was because enough fluid leaked out that the pressure was dropping (even though the jacks were still retracted). The dealer was 2 hours away so I decided to try and fix it myself. I thought it was a bad hose but it turned out to be an o-ring that was damaged during assembly. I got a new o-ring at the auto parts store, refilled the fluid, cycled the jacks a couple times and that solved the alarm problem.
Check your reservoir and make sure it is full and then look at all of your hose connections and the jacks to make sure you don't see any leaks. If you don't see any leaks, it could be an internal seal in the jack or it can be a bad pressure sensor on the power unit.
If you have the Lippert Levelers, the pressure sensor looks like this one. You should also check to make sure the electrical connection is secure because that could cause an issue.
If you are sure the jacks are secure and they won't deploy while driving, you can trip the 100A breaker and that will stop the alarm.
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