In our case it was the issue that the file format wasn't whitelisted on the actual mid-sourcing server. the issue was resolved after TechOps team of Adobe whitelisted it on their end.

Thanks for the info! Unfortunately that doesn't seem to be the issue on our end. I raised an Adobe Support ticket to see if this might be related to the latest build (9032).

I have the same issue.I've tried uploading it as an attachment but upon sending it fails. And I've tried uploading it as a public resource but it returns a 403 error.Before we didn't have this issue but it started since we're on build 9032. Anyone else that was able to resolve this?