Missing Onkyo AV receiver in devices

[stv_t]

Plan

Premium

Country

UK

Device

(HTC U11, Samsung Galaxy tab 4)

Operating System

(Android 9)

My Question or Issue

I have a networked Onkyo TX-NR818 AV reciever to which I normally redirect Spotify (Premium) to play through. I have an HTC U11 which was upgraded last week to Android 9. I also have a Samsung tablet which was upgraded to Andriod 9 some months ago. Both of which had the Onkyo appear in 'Devices' and were able to connect to and switch on or change input.

Last week Spotify was upgraded on the tablet after which the Onkyo no longer showed up in Devices when using Spotify. However the Onkyo still appeared in the Devices menu on the phone and I was able to redirect output to the Onkyo, and the tablet would show the Onkyo as the output device, I could also redirect the output back to the tablet then back to the Onkyo from the tablet.

However Spotify on the phone was automatically updated yesterday and no longer shows the Onkyo under Devices, therefore I cannot redirect output to my AV receiver.

I have cleared the cache and storage on the phone and removed and re-installed Spotify, I have also unplugged the AV receiver and restarted the router, however it is still missing from the Devices list.

How can I get the AV reciever to re-appear in the 'Device' list ?