Issues with option "Allow reviews from verified buyers only"

Hi,

my setup is like this: https://prnt.sc/jl5f56
Everything works fine with these settings.

But as soon as I tick tick the third box (“Allow reviews from verified buyers only”) then something is not right. I always get the message that only verified owners can submit a review – even when I bought the product.

1. As a logged in user who HASN’T bought a product I get the text saying “…only verified owners can submit a review”
2. As logged in user who HAS bought a product I get the same message
3. As a logged out user I get the same message

To sum it up: as soon as I tick the third box from the options it is not possible anymore to submit reviews.

What am I doing wrong?

Thank you for your help.

Thomas