Actually, Mayosis Theme is for Digital products Selling theme. It needs an “Easy Digital Downloads” plugin. As I know they are using the Easy Digital Downloads register system. Check this screenshot: https://share.msbofficial.com/DOud0NXG
if you make your plugin Easy Digital Downloads compatible then i hope this will work perfectly then.
Here is the video link: https://watch.msbacademy.com/share/mh9tobdju4lrtui3l2s4mwmbr82b6ukq