Check the following:
Make sure you have installed the MIDI plugin (and if required for your pack, the Cubase plugin) from the Stream Deck store. If you have previously installed, you can try and click Uninstall and then Install again to reinstall. This can often fix any issues.
If the MIDI controls are still unresponsive (yellow triangle), double check that you have entered the port names correctly.
The following are the correct spelling for the ports used (depending on the pack you are installing you may be using some or all of these - refer to your pdf)
StreamDeck2Daw
Daw2StreamDeck
StreamDeck2DawTrack
DawTrack2StreamDeck
If working on a Mac, make sure you have checked the box for Device is Online and the Device Name field is blank.
Ensure the correct assignments are in place for the ports.
If the MIDI Remote controls are not working, ensure that the Generic Remote is the FIRST remote device in your list.