Bug ad unit configuration not found for game id

Stacktrace below, this happened because I was using the mediation package but hadn't hit the 'use mediation' button on the Unity web Dashboard. If you're upgrading a project from using Unity Ads SDK and don't hit that button you'll get this unhelpful message despite the ad units section of the dashboard showing that, yup, everything is set up as it should be.

Code (CSharp):

1. 10-16 18:05:15.755 26935 26967 I Unity   : NetworkError:Exception raised while retrieving the Ad Unit Configuration: com.unity3d.mediation.j0: Failed to fetch Ad Unit due to connectivity issues: Request to https://mediation-instantiation.unityads.unity3d.com/v1/waterfall failed due to java.io.IOException: Instantiation Service configuration request failed with http status code 404 and server response: ad unit configuration not found for game id: 1624066, ad unit id: rewardedVideo
2. 10-16 18:05:15.755 26935 26967 I Unity   : AdsController:OnUnityAdsFailedToLoad(Object, LoadErrorEventArgs)
3. 10-16 18:05:15.755 26935 26967 I Unity   : UnityEngine.WorkRequest:Invoke()
4. 10-16 18:05:15.755 26935 26967 I Unity   : UnityEngine.UnitySynchronizationContext:Exec()
5. 10-16 18:05:15.755 26935 26967 I Unity   :
6. 10-16 18:05:15.764 26935 26967 I Unity   : Exception in loading Ad ex:Unity.Services.Mediation.LoadFailedException: Exception raised while retrieving the Ad Unit Configuration: com.unity3d.mediation.j0: Failed to fetch Ad Unit due to connectivity issues: Request to https://mediation-instantiation.unityads.unity3d.com/v1/waterfall failed due to java.io.IOException: Instantiation Service configuration request failed with http status code 404 and server response: ad unit configuration not found for game id: 1624066, ad unit id: rewardedVideo

 

Where is the "use mediation" button? Can you please take me through the steps to find it as i cant find it

 

have found "use mediation" button?? me need step too where is???