There is no code that you need to enter to be able to AirPlay to our Network Players. We have, however, had a few reports of this issue occurring previously, and it seems to have been an iOS problem that has caused it. We would suggest trying the below:
If you are getting a code request, please check 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, and is generally used on iOS devices that are part of a corporate environment.
This is accessible by going to Settings > General > Device Management > Profile Name.
Disabling just that setting in the profile should allow you to stream AirPlay to your Network Player without a password prompt. Please do let me know how you get on.