Error: BUILD_SERVER_SDK_VERSION_NOT_FOUND

https://docs.aws.amazon.com/gamelift/latest/apireference/API_CreateBuild.html https://docs.aws.amazon.com/gamelift/latest/developerguide/integration-engines-unity-using.html

The error "BUILD_SERVER_SDK_VERSION_NOT_FOUND" is suggesting that the GameLift server SDK version was not specified when you built your game server with Amazon GameLift. According to the Amazon GameLift documentation, the server SDK version is the version you used when integrating your game server build with Amazon GameLift. If you don't specify it, Amazon GameLift sets this value to 4.0.2 by default​.

You might have missed this step when you uploaded your new build. Here are the steps to set up the Amazon GameLift server SDK for Unity:

1. Download the Amazon GameLift server SDK. The Server SDK zip file includes the C# Server SDK, with source files so that you can build the SDK as needed for your project.
2. Build the C# SDK libraries. Load the C# Server SDK solution file in an IDE, and use the IDE's functionality to restore NuGet files for the project. Build the solution to generate the C# SDK libraries.
3. Check the Configuration settings in the Unity Editor. Open your game project and go to File, Build Settings, Player Settings. Under Other Settings, Configuration, check the settings.
4. Add the Amazon GameLift libraries to your Unity project. Import the libraries produced by the solution build into the Assets/Plugins directory of your project​.

If you've already followed these steps and are still facing the issue, it might be a good idea to double-check the version of your server SDK and make sure it's included in your build process.