Kokoon support gave up on this. Maybe anyone here has any clue as to why? It is not that it does not work. I do not even get the option to start the download.
Just a totally wild guess: Have a look at Settings > System > Maintenance > Enhanced hardware features. The app might require that you enable some or all of these three features. If you try this, make sure to follow the instructions at the bottom, the changes will only go into effect after a reboot.