Error 0x803f81f5 when launching AirServer.

Error 0x803f81f5 is a Windows/Xbox Store DRM error which means that your device, in this case your Xbox, could not obtain a license from the store to run this application. 
This happens if you already have 10 or more devices associated with your Microsoft account.

To fix the issue, open the devices page in your Microsoft account settings through a PC and remove all the devices that you are no longer using. Then re-launch AirServer on your Xbox and everything should start working. It appears that Microsoft does license acquisition only on the first run. 

Here is a link to the device page in your Microsoft account settings: