Possible Causes:

A valve may be "stuck" closed. If the instrument hasn't been used in awhile, it is possible that the solution is simply to clean the valves and clean any debris or buildup that may have settled on the valve piston.

To test:
Turn the instrument on and press <stop> to initiate a drain cycle. If the pressure does not drop to zero in 3 minutes, you will need to clean valves Q5 and Q6.

To clean valves Q5 and Q6:
Remove the back of the machine and clean the coils (do not get them reversed). See XT Service Procedure #5.

After the valves are cleaned and put back together, run a 10 minute extraction to see if this solved the problem. When the 10 minute extraction ends, the screen will say "Draining". Contact ANKOM if the pressure does not drop to Zero over the next 3-5 minutes.