Found five missions that do not show up simulator.

[TimA]

I need some  help with how to access some missions that I found. They are located in
the MS FSX/missions/racing folder, but they do not show up in the simulator missons page.
These racing mission are listed as    GreekXC, HoopRaceCource, JetCanyon, MindenXC,
and MP_Secret_Island_Race.

[skimmer]

It must be that way for everyone because I got same. 

[Gunfighterj]

That's Because it's a multiplayer mission. You need to go online to play those missions.

[TimA]

Thanks for the info, what I suspected. Will have to try it, they look like great flights.