Calling a java method from a second thread is not working

I have this little function calling a java (android) method:

 public static void Compose(string initialText, string url, string image, Action<bool> callback) {        
     Loom.RunAsync(() => {
         AndroidJNI.AttachCurrentThread();
         bool rs;
         using (AndroidJavaClass jc = new AndroidJavaClass("com.beavl.android.ShareTools")) { 
            rs = jc.CallStatic<bool>("share", initialText, url, image);             
         }             
         Loom.QueueOnMainThread(() => {callback(rs);});
     });                    
 }

Note: Loom is a multithreading library that worked perfectly so far for me. It's here.

And the function just doesn't work, it does nothing as if it was never called.
If I remove the Loom parts of the function, so I call it from the main thread, it does work.

I have a log on the first line of the function to be sure when it's called or not.

Any idea why i'm getting this behaviour?