It doesn’t happen to everyone that a sensor shows a tank empty when it’s full. The normal flaw is showing full when it’s empty. I suspect you have a bad connect to the bottom sensor (ground/base) so that the other higher sensors are not completing the circuit. We had a thread on this recently (can’t find it on my phone - will look again later).
Thanks to everyone who took the time to reply. The other lights, Propane battery fresh water all seem to be working just the gray.
All input is greatly appreciated, when I get back from trip I will put advice to work.