That RV has a number of options that may change small points but there are a couple items which you might check as a first step.
Do you have a light at the monitor panel, possibly on the ceiling above? If so, does it work?
It is on the same circuit as many other things and the monitor panel, so if that light works, you can move beyond checking one breaker that might be involved.
There is a breaker panel that has the 12Volt breakers on two rows, top and bottom with six on each row. So if we look at the front and count left to right this breaker should be number five on the top row. Check it if the light doesn't work!
Then there is a breaker for the level indicators on the bottom row, so check it while there and look at the number one (bottom left) on the bottom row.
Try clicking them off and then fully all the way on as they sometimes look good but need reset fully.
This is the breaker panel when viewed from the BACK side:
Click to get a better view but when looking at the front, we have to remember to switch left and right!! Just for fun!
It may be labeled but the labels often leave out lots of circuits when one breaker feeds so many as JA does, so ignore if it says it is something else as it does feed several things like water pump switch and other lights.
JB circuit is for the level sensors.
I would be surprised if it were two breakers off but then surprises are common.
What I might lean toward is there is a big plug behind the monitor panel and it may not be making good contact on all the connections.
But maybe check the easy stuff first before how to pull the panel or get to those plugs?