Hello, Imran Bashir,
Thank you for contacting us and for using XStore.
We do not give a guarantee for full theme compatibility with all existing 3rd party plugins. Sometimes, but not always, you need additionally customize the theme or plugin to make them work together. Unfortunately, it’s not possible for the author to make the theme compatible with all the existing plugins and additional customization is outside the scope of our basic support.
1/ Try to disable Single Product Builder via Theme Options and check if the plugin works as you expected.
2/ Try to disable Ajax add to cart via Theme options and do one more test.
3/ Let us know the results, and provide FTP access (you mentioned them, but did not provide them).
Thank you for your cooperation and we look forward to hearing from you soon.
Kind Regards,
8theme team