theme doesn't allow most plugins to work

I have the covert store builder theme and I’m trying to add a plugin that will allow me to display content towards the top of the page below the header content that is not just selling products. Google has the website listed as pure spam because they say it’s thin on content. I’m getting zero search engine traffic. There are many plugins that do this. I’ve tried about 20 so far and the plugins I have tried don’t function. Any ideas on how to fix this?
website is https://www.gps.overthetopdeals.us