Apple Music can't stream when connected to wifi

I have a strange problem that started within the last few weeks - every time I try to play anything through apple music at home when connected to wifi it comes up with "Connect to wifi or mobile to play music".

If I switch wifi off and try to play music it works fine using 4G/3G. But switching wifi back on again comes up with that message.

Everything else on my phone works on my wifi (I'm typing up this question summary on my phone right now via chrome). But for some reason apple music does not.

Also just to let you know the OS is updated to 11.4 and all the apps seem up to date.

Please advise as to what I could do to fix this issue. I don't want to have to find alternate means of streaming music.

Thanks!