This picture can't be flagged.
It used to be impossible to vote on missing images that had been flagged, which is sort of related: Can't vote on missing images that have been flagged
But it's never been possible to flag 1x1 images (which this is). It was mentioned in that thread and again in 2016: Non-existent author image
So it's still a problem that you can't easily flag 1x1 images. Perhaps that will be addressed now?
In any case, here's a link where you can vote on this image: https://www.librarything.com/pic/8535953, and now that it has been flagged you can vote on it in the flagged gallery https://www.librarything.com/gallery/flagged