Hi Michelle,
Sorry to hear that you ran into this issue. If your course is getting stuck while loading, there's a possibility that corrupted data is preventing the course from working properly. I'd like to gather more information to figure out what's happening:
You can also check out this article which explains how to reduce the risk of encountering file related issues when working in Storyline 360:
Follow These Tips to Reduce Your Risk of Corrupting or Losing Project Files
If working locally and importing to a new file don't help, please reach out to our support team here so we can take a closer look at your project file to restore its functionality.