If you are using a mac computer, and you find that a course will not load, first make sure cookies are enabled, as per our other support article.
If that doesn't work, there are two further things you can try.
First - try to update the OS, to ensure you are using the most up-to-date system. Our software works best on later versions if iOS.
Second - try to use the software on a different browser. Safari may occasionally get 'stuck', so try to use either Chrome or Firefox, and this may resolve your problem.