Hi Julia,
I received the email.
The APP ID and the keys look good. No issues in that.
It seems like a Facebook is not returning the correct count for external people.
I saw the count using other tools outside, they all return 0.
This is some problem on the Facebook side and beyond our control.
I think you can ignore this for now and have a look after some days.
You can also manually check the count on this page – https://www.sharedcount.com/
If you can see a count there, your website should also show one.
Thanks,
Aakash