The Low Voltage message could be a clue. Most coaches have a Bussman-type breaker off the house batteries for the power to the leveling motor. If that breaker trips, is defective or there are loose / corroded connections, you will get a Low Voltage error even when the batteries are fully charged. You want to find that breaker and check to make sure it is not tripped. If you can't find it you can try to measure the voltage going into the motor solenoid to see if you have 12V.
Now the Jack Down message could be another clue as well. There is usually a pressure sensor on the hydraulic power unit. If that sensor goes bad, the system will think there is not enough pressure to keep the jacks retracted and it will send an error code saying the jacks are down (even if they are retracted). Not an easy way to test that the sensor is working properly as far as I know short of swapping it out. I ended up replacing one on my 2018 Outlaw a few years ago.
Assuming their are no signs of visible leaks at the jacks or hydraulic lines, then it could also be a bad control unit.
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