Hello, Srinivasan
Thank you for using our theme.
We have investigated the issue with the plugin and have determined that it is independent of our theme. To demonstrate this, we have included a video of when a default WordPress theme is activated ( https://gyazo.com/04390af7b3a6479558fe3db02484541e ).
The code in the documentation is for our Single Product Builder ( https://prnt.sc/3TodCbPPsdC0 ), however, the builder is disabled on your site.
We hope this information is helpful.
Kind Regards,
8theme team