I tried many solutions and launcher options (run as admin, add -ui option). On my wife pc all setup was fast and work perfect.
But on my W7 x64 I get error:
----- C&C:Online Launcher Start -----
Game: Red Alert 3
Red Alert 3 Install Path: G:\SteamLibrary\steamapps\common\Command and Conquer Red Alert 3\
Started game with: "RA3.exe -ui"
Caught CREATE_PROCESS_DEBUG_EVENT from Red Alert 3. Detaching...
ERROR: game.dat process not found.