I'm not sure about the install process for the cd boxed version, but make sure there is a line in the fsx.cfg under [Main] to include MyTraffic. Example below. If you have fsx Deluxe you can activate the traffic toolbox within MyTraffic. You'll need to modify the dll.cfg file to do so. I've included an example below.
[Main]
User Objects=Airplane, Helicopter
SimObjectPaths.0=SimObjects\Airplanes
SimObjectPaths.1=SimObjects\Rotorcraft
SimObjectPaths.2=SimObjects\GroundVehicles
SimObjectPaths.3=SimObjects\Boats
SimObjectPaths.4=SimObjects\Animals
SimObjectPaths.5=SimObjects\Misc
SimObjectPaths.6=MyTraffic\Aircraft
Launch
dll.xml
False
False
Object Placement Tool
False
False
..\Microsoft Flight Simulator X SDK\SDK\Mission Creation Kit\object_placement.dll
Traffic Toolbox
False
False
..\Microsoft Flight Simulator X SDK\SDK\Environment Kit\Traffic Toolbox SDK\traffictoolbox.dll
Visual Effects Tool
False
False
..\Microsoft Flight Simulator X SDK\SDK\Environment Kit\Special Effects SDK\visualfxtool.dll