MainStage: Remove 'Unassigned Blocked' for MIDI CCs?

How to remove Channels 1-16 Unassigned Blocked in mainstage?

I am assigning a foot controller to various aspects of my concert, but some of the controls are being blocked by this setting:

How do I remove this block? The Screen Control Inspector when this is selected says "Nothing Selected".

Concert Settings has MIDI -> Program Changes -> Send unused program changes to Channel Strips checked. Unchecking it does not change anything for the incoming messages.

Incoming messages being blocked are on Channel 1, CC0, CC1, CC9 and CC17.

Incoming messages that are assigned and not blocked are Channel 1, CC2, CC3, CC4, CC5.

I really don't understand what is happening and why I can't create new assignments for CC0, CC1, CC9 and CC17.