Propane supply

[DennisB]

Hi. We are on first extended trip in our new 2020 trail manor 2720QD.
Last night the propane ran out so I went out front of the trailer and flipped the lever that says “supply” over to the other tank and there was no propane in it either. So apparently both tanks had drained. Very inconvenient on a chilly night.
Today, I got the tanks refilled and reinstalled them. Turning only one tank on, I put the supply valve in several different directions and it made no effect on the flow of propane into the trailer. So I can only assume that this valve either doesn’t work or is simply for decorative of purposes. Because the dinette part of the trailer extends out over the propane tanks it’s a bit of a hassle to change the tanks on short notice like late on a rainy night or something like that.
For the time being I will just turn one tank on and when it has drained climb underneath the trailer and turn the other one on by hand. It’s a little uncivilized and I’m looking for a better solution.
Any suggestions would be appreciated. Is there any add-on propane level monitoring systems that work well? (The little gauges on the tanks don’t seem that accurate)

Thanks,
Dennis