Could be fuse if power up to fuse but not beyond.
See the Ask thetford fill in the online form if you can't get a solution with the pdf's.
Another tip to bear in mind for future....if you turn on the cabin /toilet lights or saloon light/s and press the pump button and lights 'Dim' then come back on release of pump switch/button then that's a sure sign of a jammed pump. You can usually access the impeller at base of pump with a small screwdriver turn it until it feels free. Alternative replace the pump.
Thetford pdf accesss :
UK www.thetford-europe.com
Australia www.thetford.com.au (Even get request from Australian campers)
Australia site has stockist list.
HOME PAGE SELECT ENGLISH {if in Australia forget this selection)
NEXT PAGE SELECT CUSTOMER SERVICE (top line)
NEXT PAGE SELECT USER INFORMATION (left of pic) also 'Ask thetford' is on this page.
NEXT PAGE SELECT REPAIR INSTRUCTIONS (left of pic)
NEXT PAGE SELECT BUILT IN TOILETS [top right of pic]
NEXT PAGE SELECT This is where you select your toilet range. Search alll if unsure of type/range
NEXT PAGE PDF Files You should be in the pdf folder list on your Thetford toilet. Start downloading.
Bob
January 2012