Error publishing upload a SCORM package I've translated using localisation

That error suggests your zip doesn't contain the necessary imsmanifest.xml file:

If you zipped it manually as opposed to using the button Storyline offers immediately after publishing, is it possible not all of the published output was included in the zip?

If you zipped it manually, I also wonder if you zipped it by right-clicking on the folder of the published output as opposed to lassoing the contents of the published output folder. The imsmanifest.xml needs to be top-level in the zip, meaning when you double-click the zip to open it, you should see a list of files like those above in my screenshot.

If instead you open your zip and just see a folder that contains your published output, then the zip was incorrectly made and you'll need to re-zip the contents. I don't know of any LMS that goes hunting down into folders for the imsmanifest file. It's either there at the top of the zip or the zip is invalid.