SCORM 1.2 package gives "imsmanifest.xml not in root" error when uploaded to LMS

Hi all,
I'm working on a Rise 360 course for a client who uses SCORM 1.2 regularly. I exported the course as SCORM 1.2 from Rise (via Export > LMS > SCORM 1.2), downloaded the ZIP file, and sent it directly (without unzipping or modifying anything).

However, when the client uploads the ZIP to their LMS, they get this error:

"An imsmanifest.xml file was found but it was not in the root of your zip file, please re-package your SCORM."

I’ve checked the ZIP file myself and confirmed that the imsmanifest.xml is in the root directory (not in a subfolder). I suspect the problem might be happening during their upload process, but I want to make sure I didn’t miss anything on the Rise side.

Has anyone experienced this before? Any idea what could be causing it or how I can guide the client more precisely?

Thanks in advance!
Alice (from Portugal)