Got exception while implementing GooglePlayLicenseVerification(lvl) plugin.

I am trying to implement GooglePlayLicenseVerification on my app.

I downloaded the plugin from asset store and found readme file from https://github.com/Unity-Technologies/GooglePlayLicenseVerification I succeed to test with sample code and sample public key. But when I imported the example scene in my existing app and only changed the public key. I got the following exception.

 I/Unity   (16134): Exception: No such proxy method: UnityEngine.AndroidJavaRunnableProxy.run()
 I/Unity   (16134):   at UnityEngine.AndroidJavaProxy.Invoke (System.String methodName, System.Object[] args) [0x00000] in :0 
 I/Unity   (16134):   at UnityEngine.AndroidJavaProxy.Invoke (System.String methodName, UnityEngine.AndroidJavaObject[] javaArgs) [0x00000] in :0 
 I/Unity   (16134):   at UnityEngine._AndroidJNIHelper.InvokeJavaProxyMethod (UnityEngine.AndroidJavaProxy proxy, IntPtr jmethodName, IntPtr jargs) [0x00000] in :0 

I think the exception coming from

m_LVLCheck.Call("create", m_Nonce, new AndroidJavaRunnable(Process));

this line in the CheckLVLButton.cs

How can I solve this? Should I recompile the jar file? Any advice would be greatly appreciated.