Android Oreo unable to see devices

[derekcrew]

Plan

Premium

Country

UK 

Device

Samsung Galaxy S8

Operating System

Android Oreo

My Question or Issue

On my home network I have 3 Amazon Echo Dots on Wifi and a Windows 10 PC with Spotify on ethernet (as well as other devices from time to time).

Some months ago (last year?), when using Spotify on my Galaxy S8 at home I was able to see the other networked devices, and select them to play music.

At some point I lost that functionality - the devices are no longer visible on my mobile.

However, if I play music directly on those networked devices I get a message in Spotify on my mobile, asking whether I want to continue playing on that device or on my mobile.  If I continue on the network device, I can then control the music on that device via my mobile.

Any suggestions as to how to have my mobile 'see' the network devices again, rather than using this workaround?

All wifi network devices are using the same network SSID and frequency.

Other mobile phone utility apps can see the desktop PC and its contents via the network, so I don't believe it's a Windows/Firewall issue.

I have tried re-installing Spotify on my mobile phone.

Many thanks.