Hello Lucy,
Happy to help!
If your other courses are working fine, then it's a possibility that the issue you're experiencing is specific to the one course that isn't loading properly. You can troubleshoot the behavior by publishing and uploading your course to different environments to see if the issue will be replicated. Here are some tests that you can do:
If your course works in Review 360 and SCORM Cloud, try re-uploading your course in your LMS/web server to see if this helps.
If your course still doesn't load in Review 360 or SCORM Cloud, would you be willing to share a copy of your project file here or in private by opening a support case so we can take a closer look at what's happening? We'll delete it when we're done testing!