Hi all, We have an on-premise application, with dev, UAT and Production environments. In UAT and Prod, we have 2x web apps (load balanced) + 1 integration server. The files for the app are on the integration server The 2x web apps refer to the shared folder on the integration server in the uploaded files path of the Mendix service console/ We have a service that calls an API to retrieve a document, it will then download and open in the browser and delete after downloading. This works in Dev fine. In UAT, the same process, same user roles, I get a File does not exist for key: 0. When looking for similar issues, I can see other people getting this, but in those instances, the key has the full file ID/GUID. The folder structure I can see for the files is data\file\XX\YY\ with the file name being XXYY.... So what stands out to me, is in my error, I don't have this key, it's just a 0. Other files I have tried download fine. Unfortunately for UAT and Prod we have to rely on a 3rd party to the deployment for us and I was not present during the deployment, so I was unable to see what was done. I am led to believe that maybe some folder permissions were amended in order to get the application to start as it was not deployed with the service account used to run the service. I've reviewed the project folders + shared folder used for storing files and I can't see anything obvious. The service accounts used to run the Mendix service has modify permissions on the shared files folder. The app is in a folder called MendixApps\ I can't see permissions for the service account here. I'm leaning towards this being a possible issue. The shared folders/files are on D:\Files and the service accounts do have access here. Has anyone had any experience of this specific issue, with the key: 0 because this appears to be different to other issues of the similar vein.