Seem to be having the same issues as a lot of users
Red Alert 3 Steam version
Ca public key patching routine failed when i start through the launcher
Windows 10, ran with and without xp compatibility mode
----- C&C:Online Launcher Start -----
Game: Red Alert 3
Red Alert 3 Install Path: C:\Program Files (x86)\Steam\steamapps\common\Command and Conquer Red Alert 3\
Started game with: "RA3.exe "
Caught CREATE_PROCESS_DEBUG_EVENT from Red Alert 3. Detaching...
Found game.dat process. PID 3428
ERROR: game.dat process not found.
----- C&C:Online Launcher Start -----
Game: Red Alert 3
Red Alert 3 Install Path: C:\Program Files (x86)\Steam\steamapps\common\Command and Conquer Red Alert 3\
Started game with: "RA3.exe "
Caught CREATE_PROCESS_DEBUG_EVENT from Red Alert 3. Detaching...
Found game.dat process. PID 342810028
*** Starting CA public key patching routine ***
ERROR: Reading process memory failed. Error: Only part of a ReadProcessMemory or WriteProcessMemory request was completed.
ERROR: Reading process memory failed. Error: Only part of a ReadProcessMemory or WriteProcessMemory request was completed.
ERROR: CA public key differs from expected value. Not patching.
ERROR: CA public key patching routine failed.