The only thing that comes immediately to mind is the main disconnect switch (if outfitted). Do any of the other 12v devices work, i.e., lights?
If the disconnect is on, all the fuses are OK, then you can test the pump motor by running a jumper cable (cheap extension cord with the ends cut off will work; just be mindful of polarity) direct from the battery to the pump and see if it runs then. If it runs with the jumper and all the fuses are OK, then most likely a break in the wire...