I've experienced the same problem with my iMac. Yesterday, I called Support because of this problem and spent 2 1/2 hours talking with the Senior level support person, who was very surprised to hear about the problem and indicated she had never heard about it. At the end of our conversation I stated..... Has the new operating system removed AirPlay? There was no response from the technician, she moved to a different subject. Today, continuing my effort to discover just what the problem was, I discovered the RING App had the airplay icon and it's functioning. But so far, Chrome and Safari are not supporting Airplay. Which has me wondering, is it an application or an operating system problem? The other thing I looked into, which I read online, was going into system preferences, then Displays. At the bottom of the screen there's an airplay display drop-down, click on the drop-down, select the Apple TV that you want to communicate with. It took about 20 to 30 seconds for the computer to react to that selection. My terminals then went dark and then came back on. Started streaming a movie but there was no icon presented in Chrome nor in Safari. After a short period of time, the airplay display option change back to off. Tomorrow, I'll reestablish a conversation with the senior support person to discuss the RING App.