Best answer by Ryan S
We're looking into this one those steps above seem to be doing the trick where we've seen this issue. Tunnie, if you're still getting a code request, please check again that you have 'AirPlay outgoing requests pairing password enforced' toggle setting disabled? This setting is usually part of a Device Management (MDM) profile that is added to and configured on iPhones and iPads. Again, this is accessible by going to Settings > General > Device Management > Profile Name. It's generally used on iOS devices that are part of a corporate environment.
Disabling just that setting in the profile should allow you to use AirPlay to the Sonos player without a password prompt.
Let us how it goes.