Yesterday’s Apple TV update broke the awesome PlexConnect hack that allowed a fully-functional Plex client on non-jailbroken Apple TV 2 and Apple TV 3. It seems that Apple fixed the Trailer app vulnerability. According to Cult of Mac:
Apparently, the reason PlexConnect worked was because, uniquely on the Apple TV, the Trailers channel piped all of its video over HTTP, not HTTPS. By just adding an ‘S’ to the end of that protocol, PlexConnect was seemingly broken for good.
Fortunately, a security developer Paul Kehrer posted a detailed tutorial on how to fix the broken PlexConnect hack. You will need a micro USB cable to attach to your Apple TV and the Apple Configurator (Mac) or iPhone Configuration Utility (Windows or 10.6 Snow Leopard).
You can also check the Plex forum for mas info.