New SCORM file will not launch in Litmos LMS - Litmos say issue with CORS, but we are using SCORM not xAPI

I'm quite experienced in developing Storyline and have been exporting to SCORM, and our LMS, for a number of years. However, I'm stumped on this one.

I have recently used a template available from Articulate, and am exporting as normal to Scorm 1.2. I have the usual tracking options switched on (course completed by trigger), and have no LRS settings. In fact there is nothing different to how I am publishing this file, compared with other courses I create. The only difference is this one is using a new template.

The file will not load in my LMS. After reaching out to Litmos, they asked me to check my CORS policy - I have no clue what this is. When I pressed further they said the following:

"I have investigated this from my end and I would like to let you know that CORS policy is something being blocked as it is calling your URL from your SCORM file. Your SCORM file tries to reach the dispatch by calling your URL and that is causing the issue.

Can you please reach out to your Storyline support and see if they can help you on this? as we do not have control over your SCORM settings."

Can someone help? As far as I know, CORS is something to do with javascript. We do not use JS in our Storyline modules. What else could this be?

For testing purposes, the course plays fine in Scorm Cloud

Thanks in advance!