Hi @PiWizard, please start the casting feature once by going to Settings > Screen Mirroring > iOS. This enables AirPlay, Google Cast and DLNA. After the first start, you can go back to the home screen, the casting feature will always be available in the future. Also make sure your PicoPix Max is connected to the same network as your phone or Mac.
In addition to AirPlay, Google Cast and DLNA, PicoPix Max also supports a 4th option: Miracast. It’s most often used for Windows and Android devices to cast the entire screen, and doesn’t require the PicoPix to be on the same network as your phone. To use Miracast, you’ll need to start this service every time you wish to mirror your device, by going to Settings > Screen Mirroring > Android.
And specially for YouTube, you have a 5th option: Link via WiFi or Link via TV Code. To enable this feature, open the YouTube app (SmartYouTubeTV in the current firmware), go to its Settings and select Link via TV code (recommended). Then you’ll be able to use YouTube on your phone to cast a video to the PicoPix.
Hope this helps.