Hi @Marius_Van_Rijckevor welcome to Zwift forums.
Those symptoms sound like the Launcher app is not finding the correct folder location for the game app. This can happen if files get corrrupted. Uninstalling / reinstalling may not remove the corruptions. So instead, try this:
I have posted two suggestions in this previous thread. Would you try the procedures in both of my responses?
Please let us know how it worked out?