I had the same problem, take the water tank out, look on the bottom, is there a red seal on the tank? If not, its either lost (can get new one here http://www.4bissell.co.uk/cgi-bin/product.pl?PID=947370&query=7920%2de) or more likely its stuck in the bottom, if it is get a screwdriver and prise it out of the base and put it on the tank. All should be well. Regards Paul
Paul, January 2010