check pressure switch  chamber for a BLOCKAGE 
remove the top look for a round switch with wires and  a plastic pipe attached(pipe MAY HAVE come OFF reattach problem solved.If pipe is on REMOVE it, now blow hard down the pipe if you go RED TUBE BLOCKED as the hole is very SMALL blocks with powder residue if you can't clear by blowing need to find the lower end of the pipe on the pressure chamber pull off and clear the hole reassemble pipes etc and re try machine.  No joy replace the pressure switch with a new one
                
 wirecutterman
                
 August 2008