So as the comments state this error is most likely caused by incorrect access rules configuration.
However, in 8.17 I had this error when I had the ‘Close Page’ activity in a microflow.
Removing the close page activity fixed the issue for me. Putting this answer here for reference.
This might help someone. It was access rules in my case, because I was trying to download a FileDocument directly. As (I think) access rules can't be added to FileDocument, I needed to use an inherited entity instead.
Please use inherited/generalized entity from FileDocument.
Please accept the Answere, it helps:)
I have also faced the same issue, I checked for all the access in the security and Entity access for the generalized Entity from the file document and the close page was the problem for me. I fixed and the error resolves!
For me the issue was that I hadn’t granted access to the newly created entities of my CSV exporter module to my users. Thanks for pointing me in the right direction!