if looking back in for more replies follow the info below. from what you say sounds like the flush pipe is off or there is no water in tank as bill cox says.
If you want to go manual have word with Thetford under 'Ask thetford' If your's is a C2 with the toilet roll holder to right(facing toilet then the cup that holds the roller removed is where you would refit the manual flush, it's same size as the elec flush knob other side that stays in place.
uk & europe	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 it doesn't come up)
	select 	customer service (top line) 
	select 	products  from top line
	select 	bulit in or portable which ever applies.
	select 	user information     from list on right.
	select 	repair instructions       from list on right
	select 	built in or portable which ever applies.
	select 	select your toilet series model number from right list.
		you will now be in the pdf listings for your range of toilets just select those that apply to your toilet and down load them they're free.
	as you go through watch for 'ask thetford' on left listings	
	you may not find what you want and you can send them a message.	
		
		for safety reasons which  i agree with thetford do not offer repair advice for fridges. refer to service centre
                
 bob
                
 November 2011