MacBook Air M1 volume controls don't work for 3rd party bluetooth devices

I have my MacBook Air M1 (Ventura 13.1) connected to Boom3 USB speakers.

The keyboard volume buttons (F11 & F12) do not increase or decrease the volume. They do however mute audio when set to off. The Volume Mute button (F10) also works.

Hence the volume can ONLY be adjusted from within whatever App I'm using (Apple Music, Tidal, YouTube and others all work) or on the Boom3 speakers themselves.

I don't have this issue with my iOS devices - these work just fine.

I also don't have this issue with AirPods via Bluetooth or HomePods via AirPlay. Possibly just 3rd party speakers.

Any ideas? I have restarted. You can't reset PRAM on Silicon Macs so don't suggest that.

Cheers