Did you set the Permalink Settings to post name and save changes to refresh the Permalink Settings?
if it still does not work,
Please create a temporary user with administrative role called themescode with email@example.com and email me the login details at
firstname.lastname@example.org from your Purchased Email ID.
NB: Keep the user themescode active until the issue is solved .
please provide me the link of the page where you used the plugin shortcode
Email : email@example.com