Amazon Music, Spotify and radio will only play on Sonos One when in group

There is no reason for the One not to work with your other products. 

First thing I would try is to power off your router and Sonos devices.  Power the router back on, then wired Sonos, then the One.

Do all your devices show as WM:0 in the Sonos app under About my System?

The One is WM:1

All the others are WM:0

I will try rebooting the router and players…...

The One should also be WM:0. As you have wired devices it should be connecting to SonosNet not WiFi. Do you have extenders,  access points?

Neal_8,

You can perhaps ‘force’ all your devices onto WM: 0 by removing/resetting your WiFi credentials in the Sonos App “Settings/System/Network/Wireless Setup’ that will stop your devices switching to your 2.4ghz WiFi signal.

You haven't 'disabled WiFi' in the product settings for your wired devices have you? 

Neal_8,

Another couple of perhaps useful things to check/do afterwards... 

1. Set the SonosNet channel in “Settings/System/Network” of the Sonos App so that it is at least 5 channels away from your chosen routers 2.4ghz channel. Set the router channel to a ‘fixed’ non-overlapping channel (1, 6 or 11) and a channel width of 20 MHz.
2. If using other wireless access points, set those up with the same credentials (SSID/password), same ‘Fixed’ WiFi channels and channel width as your router.
3. Finally ensure your Sonos products are at least three feet away from other WiFi connected products (where practicable), particularly any Sonos wired device connected to the main router.

I am unable to disable wi-fi on the One.

I connected an ethernet cable to the One but still unable to disable wi-fi. But it is now WM:0. But problem still exists, i.e. can only stream to the One if it’s grouped with one of the other players.

Yes, they all have wi-fi disabled.

All the wired players are connected to the router via homeplugs.