Sounds quite indicative of not having Simconnect not installed or "talking to" the aircraft.

Try this... in the P3D root folder, locate:

\redist\Interface\FSX-SP2-XPACK\retail\lib\SimConnect.msi

Execute the Simconnect.msi. Not much will happen in the way of prompts or anything but it will no doubt install. Open up P3D and let us know if the problem is solved.

By the way, this also happens with the P3D version of the 777 so it really doesn't have much to do with using the FSX version. Odd.