If your knob or fader is not responding to a midi assignment it might not be capable of sending midi, or it may not send it reliably. This all depends on the keyboard itself. You will want to check the user manual for that keyboard to see if it has that functionality. If it does, you may need to enable those controls to send midi data. That would also be covered in your user manual. Unfortunately not all keyboards have the functionality to send MIDI data for all controls, especially the ones with built in sounds where the keyboard is not primarily designed as an all-in-one midi controller keyboard. At Sunday Sounds we recommend using the nanoKontrol2 for additional knobs/faders because it sends midi very reliably. We also have it pre-mapped with our Sunday Keys template so it's easy and plug and play for you!
Sunday Keys Version 2
Using the Tonic Pad Player
Getting Started with Sunday Keys for MainStage
Troubleshooting Sunday Keys for Ableton
What Gear do I need?
Troubleshooting Sunday Guitar
My Song-Specific Patch is Different from the Demo
Customizing Your Song-Specific Patch
My instrument/controller isn't connecting