Right-click on the expression pedal that you have added, and select "adjust midi/trigger settings manually." The window that opens should show the controller as 11 (hex 08 expression). At the bottom of the window is displayed the midi pedal range. The minimum and maximum positions should be somewhere between 0 and 127 respectively. It doesn't matter that the numbers are not at either end of the range. For example, my minimum on one expression pedal is 21 and the maximum is 81. Hauptwerk takes that range into account and scales it appropriately.
If the message is not a control change, you may have to adjust the configuration of the CMK keyboard for that particular input. You can download a manual here: https://www.organworks.com/support/CMK- ... %201.5.pdf
Also, make note of which midi channel is being used for each expression pedal, and ensure that that channel isn't the same as is being used by another expression pedal.
If you are using a Windows computer, you can monitor the data stream using Midi-Ox, which is free to download. If you have a Mac, you can use Midi Monitor. As you move the expression pedal, you should see the CC values change within the range detected by Hauptwerk. If you are having sporadic data, or multiple streams on the same channel, that should become evident as well.
Ray