The course you're enrolled to uses a SCORM package to run and validate course progress, and this process sometimes takes time (it can take up to four minutes) and sometimes fail.
The "Saving progress" alert is shown when:
If you haven't yet completed the course, The overlay is shown as long as it takes to validate the SCORM progress with the third-party SCORM validator.
If you have successfully passed the course, then this pop-up might take a few minutes to save your progress and in the end, issue the certificate of completion.
Note: If you are stuck getting a certificate even after passing the course, reach out to us here.