Okay, with that info we can do some looking at how the power gets to the pump.
Yes, frustrating as there are so many options and little hidden things we normally don't have to get into.
But it is usually just a matter of a bit of corrosion or something has come loose along the line and we need to sort through all the possible points that can happen. You are lucky in that your year is one that as all the drawings posted in schematic form which can letus follow a specific wire from start to finish and the drawing does give locations for those connections, making it easier than just looking at the whole RV!
To better advise on how to test, what do you have on hand? A meter is a really good thing but we might need to work out other tests if no meter.
Not expecting to have the tank switch mentioned, though.
Are the breakers on the same line at the power panel labeled, so that you can locate other things on other breakers to make sure the power is getting to that breaker or can you test for voltage there?
From this chart:
We see that wire "WC" is power to compartment lights, so knowing those work, will let us assume there is power to "JA" as they are connected to the same bus bar! Not a 100% as the breaker could be bad, etc. but a place to start.
I will do a bit of looking and get back with some other info and places to start checking.
This is the wiring for your specific unit but don't let it boggle you if not used to reading them as they tend to look like GREEK!