If all else fails:

Before diving into fixes, it is crucial to understand what this file actually does. The steam-apirajas.dll file is not a core Windows system file, nor is it a traditional game asset. Instead, it is a associated with:

Errors involving this file typically occur when the game cannot verify its ownership or when the file is missing/corrupted, preventing the application from launching. Common Fixes for steam-apirajas.dll

The solution you need depends entirely on whether you are playing a legitimate copy of Age of Empires II from Steam or an unofficial version.