The symbol is a warning that the LP tank is empty or disconnected.
Verify the tank level is reading correctly on the physical tank gauge. The RVMaster system takes a resistance reading from this gauge. If the tank gauge is reading okay, check to see that the wiring connection to the Node is good. Between the LP tank wire and LP tank ground wire, there will be a resistance between 0-90 OHMS - 0 being empty and 90 being full. On the XB-4 connector, PIN 5 is ground and PIN 12 is the LP gauge wire.
If you cannot read a resistance or read OL for open load, the RVMaster system cannot read the resistance and the wiring will need to be investigated.