If you are unable to use AirPlay on your Apple device, it could be due to a few different issues. Apple has put together a great article that helps explain the different issues and how to resolve them.
You can find their article here: https://support.apple.com/en-us/HT204291
Note: If problems persist, the problem could be with the Apple device. Apple Support can be contacted here: https://support.apple.com/contact.