I installed DS Audio on my iPad and recently received “you are not authorised to use this service” error. I knew that the user/password was correct and I could use DS Audio from my Android phone. Turns out I recently enabled “Auto Block” in the network services of my Synology server. Sure enough my iPad’s IP address was there listed as blocked. I removed it from the Block List and all was fine.
Solving “you are not authorised to use this service” when using Synology DS Audio