Plausse That knob you’re holding in your hand, shouldn’t be there but on the valve. If it screws off like that, it’s because the circlip has bent and come out of the groove you see at the end of the valve stem. As you unscrew the knob, it pulls that valve open. Close it too tight/or open it too har and the circlip bends and eventually falls off. Should be an easy fix.
Take another photo of the other end of that knob…you should find a cap you can prise off.
The system works in a similar way to this video I did for the Lelit MaraX
