I CAN NO LONGER UPLOAD FILES THROUGH DEVICE PORTAL
It is really a strange thing that only recently I can no longer upload files (csv, img, or any) through device portal to any deployed applications. I tried it on all my three HoloLens, and I tried it with all kinds of browser possible, and I do believe I configured everything to be accessible like developer mode, no firewall, etc.
But it ends up with the error when I click Upload button every time: "Failed to upload file. Error:[object Object]"