When I activate the plugin https://wordpress.org/plugins/groups/ at the same time as CoursePress, all the virtual pages (like login, register, dashboard ...) are not working anymore.
Can you fix it somehow?
I was able to locate the exact line in the Groups plugin that causes the problem. I hope this will help you fix it.
The problem is gone when I remove line 70 from groups\lib\access\class-groups-post-access.php:
add_filter( "the_content", array( __CLASS__, "the_content" ), 1 );