By default, Windows Store Applications are not allowed to send network traffic to the local Computer (localhost 127.0.0.1)   To circumvent this restriction you need to allow loopback for Emby Theater in Windows.   To do this, just download the "Windows 8 Loopback Exemption Manager" https://www.telerik.com/fiddler/add-ons   Once downloaded, just run the Windows8LoopbackManager.exe file. Look for Emby Theater in the list of apps. mark the checkbox and click save.   Now go back to Emby T