I was just replying to you…
And I was going to ask if you had switched to the Storefront theme.
Unfortunately this points to there being either js script conflicts with the theme, or the theme is not properly WooCommerce compatible.
If you want to send me a zip of the theme I can look on one of my dev sites; however, all I would to be able to tell you is perhaps *what* the issue is, but I will not be able to solve it. That would be up to the theme author.
When I look up that theme, I see that it claims WooCommerce compatibility.
What you are describing sounds more like a js conflict.
I wish I could tell you how to resolve this, but each theme author chooses to code differently, and once in a while they choose to use certain coding practices that will cause conflicts with other plugins. One of the popular themes on the market, Divi, does this also- and it is damn near impossible to get WC Vendors Pro working right with Divi because they disable certain scripts form being executed on the pages. It is strange.
Short answer: as much as I hate to say it, I think you need a different theme.
I can guess your next question would be recommendations.
This one is tough.. but here are a few I know work:
-Storefront (of course.. yeah… but it is BORING. 😉 )
-Kleo by SevethQueen (has buddypress and bbress integration)
-Social Marketplace by BuddyBoss (if you want a social website with lots of interaction.. this is the one to use right now. Buddypress & bbpress integration plus special wc vendors pro styling.. like vendor shop search & categories, favorite stores, etc.). We have a group on facebook, too, for this theme: https://www.facebook.com/groups/OneSocialMarketplace/
Other themes work… these are just the three I have found work best and that I know currently 100% work with WC Vendors Pro.