OnMessageReceived not called in WearableListenerService

The error message you have:

app does not match record's app key: AppKey[com.myapp,c3f31717fa35401056c20a2798907f1232efa75e] != AppKey[com.myapp,f36e726eefc7e528db26a1c25f6fbf2f93dacd70]

Indicated that your apps are signed with the different keys.
Package names of phone and wearable apps are the same - that is good, but they also need to share the same signature. This is the reason why messages cannot be delivered - wearable apps are recognized as "part of the same app" based on the package name and signature.

Please make sure that you have both apps signed with the same key. If you are testing the autoinstallation feature please make sure to uninstall the debug version of wearable app from watch emulator.

Use an asyntask to send messages as they will block the ui thread. Also you need to call the await method. To get the apps to have the same key, you need to use build variants with gradle.

public class SendMessageTask extends AsyncTask<Void, Void, Void> {

    @Override
    protected Void doInBackground(Void... voids) {
        NodeApi.GetConnectedNodesResult nodes =
                Wearable.NodeApi.getConnectedNodes(apiClient).await();
        for (Node node : nodes.getNodes()) {
            Wearable.MessageApi
                    .sendMessage(apiClient, node.getId(), "/start/MainActivity", null)
                    .await();
        }

        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);
        Toast.makeText(MainActivity.this, "Message Sent", Toast.LENGTH_SHORT).show();
    }
}

I had the same error, my fault was that the "wear" module's package name was not the same as the app's.

BAD:
[module: app] es.voghdev.myapp
[module: wear] es.voghdev.myapp.wear

GOOD:
[module: app] es.voghdev.myapp
[module: wear] es.voghdev.myapp

Made me waste so much time!! >:-(