Sorry to hear this, Bram!
What I would recommend doing is first updating the version of The Events Calendar on your site to version 4.4.0.1, the most recent version.
1. Once that’s updated, you should be able to do a manual import from the Facebook pages and events you specify—if you do this, what do you find? Do any events successfully import?
2. If not, then what if you do a manual import of a different Facebook page or event? What I mean is, basically do a test import of a Facebook event or page you have not imported before. Does this import work well?
Let us know what you find!
Thanks,
George