There are three possible solutions for this issue.
First, disconnect and reconnect your air compressor. Make sure it is attached properly.
Second, make sure your filter press’s end plate is installed so that the holes are toward the bottom. In the future, never remove the End Plate from the press in order to prevent potential mis-installation. Only remove the waffle plates and window plates during cleaning.
Third, verify that the T-Valve on the Filter Press is in the correct position. For a more detailed explanation of how a T-Valve works, please see our video below and/or see our T-Valve article.