This topic contains information on how to diagnose and fix common errors. It is divided into sections based on error codes or log messages.

## Response code 400

    Connecting to: https://performanceparameters.googleapis.com/v1/applications/...
    TuningFork:Web: Response code: 400
    TuningFork:Web: Response message: Bad

You can get this error if your API key is invalid. See[Enable the API](https://developer.android.com/games/sdk/performance-tuner/custom-engine/enable-api).

## Response code 403

    TuningFork:Web: Connecting to: https://performanceparameters.googleapis.com/v1/applications/...:generateTuningParameters
    TuningFork:Web: Response code: 403
    TuningFork:Web: Response message: Forbidden

You can get this error if your API key is not enabled or you made an error when restricting the API key (for example, you used the wrong certificate or hash value). See[Enable the API](https://developer.android.com/games/sdk/performance-tuner/custom-engine/enable-api).

## "No parameters: no fidelity parameters" warning and "java.lang.NoSuchFieldError" shown in logs

    TuningFork:FPDownload: No parameters: no fidelity parameters
    TuningFork: java.lang.NoSuchFieldError: no "[Landroid/content/pm/ApplicationInfo;" field "applicationInfo" in class "Landroid/content/pm/PackageInfo;" or its superclasses
    TuningFork: Could not get fidelity params from server : err = 4

These are harmless warnings emitted by the Tuning Fork library when checking to see if the app has the debuggable flag set. While verbose, they are harmless and are not indicative of a problem in the integration of the library.**You can ignore these warnings**.