To fix “Steam must be running to play” error in Tomb Raider, try this;
- Open Windows registry editor.
- Go to HKEY_CURRENT_USER > Software > Crystal Dynamics > Tomb Raider > Graphics
- Edit “RenderAPI” entry.
- Set its value to “9” (In my case, it was 0 and that was the problem).
- Launch Tomb Raider.
That’s all. Enjoy 🙂