This is the standard fix for almost all Steam-related launch failures. It forces Steam to check every file in the game folder against the server and re-download any that are missing or corrupted.
Instead, wait one hour (server replication delay), clear your cache, log in via a hardwired connection (not Wi-Fi), and try again. If the error persists after 24 hours, call the FAA Help Desk at (Option 4, then Option 2). Have your announcement number and the exact timestamp of your application ready. I Am An Air Traffic Controller 4 Application Not Found
Do not use the old shortcut.