Why do I get Error: Ambiguous Match Found (Non-Mediation PSR in use)?

In the Unity Editor, you might see the console throw an Exception that is similar to the following example:

  AmbiguousMatchException: Ambiguous match found.

  System.RuntimeType.GetMethodImplCommon (System.String name, System.Int32 genericParameterCount,
  System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder,
  System.Reflection.CallingConventions callConv, System.Type[] types, System.Reflection.ParameterModifier[]
  modifiers) (at <316d36b1472c4d88ab1721a02433c966>:0)
  
  System.RuntimeType.GetMethodImpl (System.String name, System.Reflection.BindingFlags
  bindingAttr, System.Reflection.Binder binder, System.Reflection.CallingConventions
  callConv, System.Type[] types, System.Reflection.ParameterModifier[] modifiers)
  (at <316d36b1472c4d88ab1721a02433c966>:0)
  
  System.Type.GetMethod (System.String name, System.Reflection.BindingFlags bindingAttr)
  (at <316d36b1472c4d88ab1721a02433c966>:0)


  System.Type.GetMethod (System.String name) (at <316d36b1472c4d88ab1721a02433c966>:0)

  GooglePlayServices.UnityCompat.GetUnity56AndAboveApplicationIdentifier (UnityEditor.BuildTarget
  buildTarget) (at /Users/smiles/dev/src/unity-jar-resolver/source/PlayServicesResolver/src/UnityCompat.cs:357)
  

This error can occur if you are using Unity Editor 2021.2 or later, and you are using either:

• A version of PlayServicesResolver that was provided in Mediation 0.1.1 or earlier
• A version of PlayServicesResolver that was provided outside of Mediation

To resolve this error, complete the following steps:

1. Upgrade to the Unity Mediation SDK 0.2.0 or later, and then close your project.
2. Delete the Assets/PlayServicesResolver folder in your project.
3. Reopen your project, and you will be prompted to install a version of PlayServicesResolver that is provided with the Mediation package. Install this version of the PlayServicesResolver.

For more information, see the Unity Mediation documentation.