You have assigned a Content Template to display single product posts with ("Courses"), but if you edit the template you will see that it is empty, so there is nothing to output.
Disabling Views means that the template is not used and your theme generates the product content.
If you don't need to modify what the theme outputs, delete the Content Template (or unassign it from products).
The problem is that you have this content template assigned to your products. hidden link
From what I can see is that this content template is empty, so what you can do is to delete the template or unassign it from your product post type under the usage tab.