i made an AdManager script now when i start my game error pop ups how do i fix it?

Unity Services
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1

initializationListener is null, you will not receive any callbacks
UnityEngine.Advertisements.Advertisement:Initialize (string)

2

Hello,

When you add IUnityAdsInitializationListener to your class, you’ll need to implement callback methods, OnInitializationComplete and OnInitializationFailed.
https://docs.unity.com/ads/en-us/manual/InitializingTheUnitySDK

Script reference is here: Unity Ads SDK API reference