I was also unable to upload my dsyms. The script found my files and prepped them, but then failed with error: The requested resource does not exist (http status: 404)… I assumed it was my slugs, and that the project was not being found. The spelling was exact, with no spaces, but a dash between words.
The solution was to copy and paste them directly from the settings page. I assume there’s something in my system or yours that is using an em dash instead of an en dash, or some other mystery issue. But just exact spelling wasn’t (and isn’t…tried it again). It required a copy and paste. So the issue is solved, but just getting this possible org / project slug issue on this thread.