“Item does not support reviews” error on Search Console

Hello Donna / whoever else might know the answer,

I am getting this error from Search Console:

Item does not support reviews

I am still with the “old” version plugin, “book reviews”, not the “blocks” one, since I am not using Gutemberg.
And indeed the star rating does not show.

The issue is, I am also having issues transitioning to the new plugin.
Whenever I enter a block, it does not automatically populate. And the stars do not “stick”. I rate the book by the number of stars, but when I save it, they don’t stick there.