I’ve moved your post to a more relevant thread.
Please try the basic EA app steps again: sign out and back in, then check that the game isn’t hidden in your Library and that you’re using the correct EA account.
If the game is still missing after that, please contact EA Help so our support team can verify the account entitlement. When you reach out, please include proof of purchase or the redeemed code if possible, clarify whether you own Command & Conquer: The Ultimate Collection rather than Command & Conquer Remastered Collection, and mention whether this issue only affects Red Alert 3 or multiple Command & Conquer titles. Thanks!