When you want to action a "button press" using the NUACOM Desktop App that is connected to an active call, click on the IN CALL KEYPAD (highlighted in green in this picture below)

The Green call button will turn grey to let you know you are in the correct section (highlighted in orange)

& the line in the middle of the app will say "enter number to dial"

PLEASE NOTE

If you press the green call button at the bottom of the softphone when on an active call, 
the softphone will assume you wish to make an additional call or make another call out.

(This shows that the Call button was pressed before the in call keypad as it is green & you can see the line country code and the words "Enter number to dial")

When you want to action a "button press" using the NUACOM Mobile App that is connected to an active call, click on the IN CALL KEYPAD (highlighted in green in this picture below)

This will open up the In-Call Keypad so you can action a Button Press