I have the same problem. In my case, I'm trying to resize a video taken by myself on an older iPhone a few years ago. I successfully fetch the video from iCloud to my new device, but the exportSession fails immediately with the error code 17507.

Could you please elaborate on that? The video is at a URL my app is allowed to access. That's why I can copy it to another location and make things work. I don't see the difference between creating an ExportSession using the URL of the original, locally stored version of a video and the URL of its medium variant that was downloaded from iCloud. Thanks.

Nope, that didn't change anything in my case.

This started hapening to several team members of ours recently. We have no clue about what caused it.

Making those team members sign in on their iPhone's using that account once again made the problem go away.