Android menifest merge with UnityDetectHeadset

Im trying to add a plugin to out Unity project.

Plugin : GitHub - DaVikingCode/UnityDetectHeadset: Detect if a headphone is plugged on iOS & Android. . this plugin detects headset status, it works great on IOS devices, and actually when we do a build for the plugin only in Unity, it works great aswell!. The problem starts when we are trying to merge the manifest I think.

In Unity I get the following error from my Android Device:

04-06 10:06:13.333 28028-28044/? I/Unity: AndroidJavaException: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.media.AudioManager.isWiredHeadsetOn()' on a null object reference
    java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.media.AudioManager.isWiredHeadsetOn()' on a null object reference
    at com.davikingcode.DetectHeadset.DetectHeadset._Detect(DetectHeadset.java:22)
    at com.unity3d.player.UnityPlayer.nativeRender(Native Method)
    at com.unity3d.player.UnityPlayer.a(Unknown Source)
    at com.unity3d.player.UnityPlayer$b.run(Unknown Source)
    at UnityEngine.AndroidJNISafe.CheckException () [0x00000] in <filename unknown>:0 
    at UnityEngine.AndroidJNISafe.CallStaticBooleanMethod (IntPtr clazz, IntPtr methodID, UnityEngine.jvalue[] args) [0x00000] in <filename unknown>:0 
    at UnityEngine.AndroidJavaObject._CallStatic[Boolean] (System.String methodName, System.Object[] args) [0x00000] in <filename unknown>:0 

As it looks java file returns null expection. it is easy to think the problem is in the code, but again if you run the plugin alone without our project, it works, so the only thing changes in the Android manifest is probably calling it wrong. I have also added our Manifest, Please advise.

Link to my Android menifest.

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