Which method are you trying to achieve? Mapping direct to VST’s or using the in-built quick control system of Cubae?
For VST Quick controls - just go to the VST Quick controls section in Studio Setup, pick your MIDI interface as the input and then click the first control item, tick the ‘learn’ box and turn a knob.
Then move to quickcontrol2, and turn second knob, quickcontrol3, third knob etc. etc.
Then your controller should be mapped to the VST Quick control parameters. This is the most flexible way of mapping to instruments, and you learn the parameters to the quick control rack in the VSTi sidebar (on the right).
You also get pages in the VST quick controls, but crazily there’s no way of changing pages via a midi controller so you have to do it with mouse. - Annoying!
With the Arturia controllers they also have an MCU mode, so you may be assigned to that mode if you currently have control of the mixer faders and pans? - Did you set it up in this way?
If that’s the case you need to swap to MIDI mode on the controller to be able to make manual assignments.
And yes i think the current system is really quite cumbersome and somewhat limited for a modern DAW, rumours are this will be addressed in the next major update though (C11.5).