We have had a fair amount of people having issues with their courses stopping on loading at 50% so here are some checklist items:
*Are you using the correct version of Unity? 5.2.3f1? - your unity version number will be under 'help' and 'about unity' while in the editor
*Did you run through the course debug to make sure that you have all the needed pins (planted on the green) tees and no extra rogue tees or pins for holes not completed yet?
*Did you make sure there are no capital letters in the scene name?
*Did you wait enough time for the course to compile and did you get a course build completed message in the bottom left of the editor window? Looks something like this: 'CourseForge {build course4} 19 Oct 11:23:17'
In the resultant folder made by the course build do you have both an description file and a unity3d file?
If the answer to all these is yes but you still have loading issues, zip up just your problematic scene file from your project and send it to me via dropbox etc