Onkyo NS-6130 streamer with Amazon Music

Hi, I know this isn't really "DIY", but has anyone set up a Onkyo NS-6130 streamer with Amazon Music (Unlimited)? I am only getting files at 256kbps rather then HD/Ultra HD (as Amazon calls High Res). This happens using The Onkyo App (Android) and the Amazon Music App (Android + Windows 10). Amazon say you should see “HD/Ultra HD flags” to change the quality. I have not seen that on the Onkyo or Amazon App. I have FLACs on my media server, they play fine (both Streamer + Amp are capable). The Onkyo is connected to my Network by Ethernet cable and I have Fibre broadband. Has anyone else had this problem with Amazon music? Any advice appreciated……