Review Snippets Issue

I have had a warning from Google Search Console that says I have 83 issues in the Review Snippets report The issue messages include
“Item does not support reviews”
“multiple reviews aggregateRating object”
“invalid object type for field “itemreviewed”
“missing reviewed item name”

As I use your Strong Testimonials Plugin on your site, I am assuming that the problem lies with the plugin. I am not a technical expert and I have no idea how to go about fixing this issue. Can you help or at least point me in the right direction?

The page I need help with: [log in to see the link]