This app is not accessible right now and the app developer is aware of the issue.
Yes, we are aware of the issue.
Facebook makes a yearly (which feels like monthly) review of apps and they require us to provide the webpage where the app is used and explain how and when we delete the personal data "we collect".
There is no webpage, since it's a desktop client... They don't understand that concept...
And we don't collect any data, since the communication is directly between the client and Facebook servers. We don't even see the Facebook data...
When we haven't been able to provide this they have now disabled the app. Hopefully we'll very soon be able to explain the nature of the importer in a language they understand and the app will be enabled again.
But, usage of this app is quite low, and the effort required to keep it alive is quite high, so you might have to prepare for a life without this feature quite soon.