I have encountered a similar problem, Google will show rich snippets if they are implemented correctly using "site:" but they will not show it in normal results if they are not sure of the quality.
John Muller talked about this in his office Hangouts
Usually, if you make a site: consult a site, we will show the rich
Fragments if it's technically correct, so it's a good way to
double check type we can pick up the brand correctly and to not
showing it in normal search results, that's really a sign that we
Basically we are not sure about the quality of the website.
I can see that you only have 1 comment on your product that may be an indication that Google does not show the rich snippet.
I would advise you to try and get more comments. Also try products with more reviews to determine if Google does not show your rich snippet because of the quality of the site or because it does not have enough revisions.
The main conclusion here is that you have successfully implemented the rich snippets, but Google is hesitant to show them because:
- You need more comments
- You need to improve the quality of the content / site
Try to increase the trust flow of your sites is one of the most important metrics when you try to gain positions of rich snippets.