Airplay problem M4 Mm - Pioneer SC-2022 Receiver / Roku Smart TV - Always ignores receiver & goes to Roku

Macmini M4 16gb 2004 OS Sequoia 16.5.1 - Tp-Link AX3000 - Pioneer SC-2022 Receiver

• I have used various Macs including an earlier MacMini to send my music from the Mac to a Pioneer Receiver over a home wifi network, in order to give me good sound.
• The wifi network runs via NBN into a tp-link AX3000 (Archer c70 I think) modem/router
• The Pioneer receiver has never reliably recognised the Airplay 'signal' so I've always had it connected to the router via an enet cable.
• When set up as above, the Pioneer appears in the list of devices for sound and when selected in Music has always automatically turned on and connected - no problems

However, more recently it is acting strangely

• Now, even though the Pioneer shows in the list and on selection it turns on as it did before, the sound always now plays through the Roku TV and I don't understand why for previously these two were connected and all was well.

So, what have done?

• Checked all ethernet cables involved
• Tried restarting and connecting again, several times
• Tried disconnecting the Modem to Pioneer cable but then the Pioneer does't appear

Anyone out there who uses their Macmini to connect with an audio system or indeed anyone out there with knowledge in the area can you help at all? I'd very much appreciate it if someone can. Thanks for reading.