Double press for toggle button.

I have been through the FAQ's as you suggested and can see nothing causing this issue.

Please would you look at the attached and help if possible.

Did you follow the link to the FAQ? The Midi plugin FAQ, not the Cubase plugin FAQ. Section "How do I use Stream Deck with the new MIDI Remote in Cubase 12".

I can see that Cubase midi remote should be set to toggle off.

This option is not available. Mapping configuration shows Category and Name only.

OK, so it's a key command you are triggering, then Cubase has no toggle function for it.

The MIDI Remote seems to treat any value larger than 0 as "On", so you can get the behavior you want by configuring the Stream Deck button as a Toggle button with values On=127, Off=1.

Stream Deck will toggle the image on each button press, and the MIDI Remote will toggle the target control on each button press, but there is nothing that keeps the states in synch; it's a 50/50 chance that they will show the same state.