Came across a weird but simple issue, and I saw this guy had the same problem but it went unanswered:
I just finished beating my head against a wall for a good 30-45 minutes and figured I'd share in case anyone else went searching for an answer, since the error message is not descriptive or helpful.
In my case, I'd just scheduled a report with a different user than I normally did. Turns out this user wasn't set up to manage reports, so I had to do the below:
From All Settings > Manage Accounts > (User account here), make sure your account's Reports privileges look like this:
Submit those changes, run again, and you should be good.
