Users cannot 'Follow Sites' cause they don't have permission to create a personal site

Hi guys, 

I have a new SharePoint Online environment and made some changes in the settings and now my users are unable to 'Follow sites'. F12 developer tools shows me a 500 Errormessage: 

The user does not have a personal site, and does not have permission to create one.

What setting do I have to change cause I cannot find it anymore 🙂 

Thanks in advance!!