Today I wanted to check what´s going on on FB and was welcomed by this message:

It´s about a post from April 2020.
Seriously, can anyone understand what suddenly triggered the Facebook guardians of goodness?
Such things make me really happy that I don´t advertise there 
Recently, hardly anyone has been able to understand Facebook
It looks like they've implemented another one of the gazillion new checks they add to the algo every day, and it checked all posts to date and your post was one of the lucky winners that got flagged by the new check (yay!)
No doubt about it - FB is unpredictable.
Amy