Frans,
Here is where you enable anonymous users in Studio Pro:
Hope that helps,
Mike
I overcame this issue simply by deleting the Native Profile (it showed as a third tab in the Navigation menu after Responsive and Hybrid phone app online). Hope this helps!
Thank you Mike. I have tried the solution you describe, but it doesn't work. I suspect I have to synchronize this setting with the developer portal, but I do not know how to do that, can you help me with that?