I do not have problems listening to tunein radio or tracks from my NAS, it seems to only be Amazon. It would suggest that the problem is not local to my network but I am happy for someone to provide a better insight.
I raised this in https://en.community.sonos.com/music-services-and-sources-228994/unable-to-play-music-6818176 but was unanswered.
I have since submitted another diagnostics 111914164 as was wondering if someone could help?
Best answer by Keith N