When a course is frozen it is often a result of a file that did not download correctly, often due to an internet connectivity issue.
To correct this we have to delete the problematic file and re-download it by doing the following:
Clear your browser history (specifically any downloaded files)
Fully close your browser (settings may be applied when the browser is completely closed).
Open the browser again and log back in with your username and password.
Resume the course where you have
If this this does not solve the issue please confirm that you are using an approved browser to access the course.