MessagingCenter not working

I had this Android App working. Then I started working on another branch, and today I continued on the Android App.
But it is no longer working. Reason is the MessagingCenter no longer works.
I have this at one location:

        MessagingCenter.Subscribe<App, FCM.NETStandard.Models.Message>(App.Current, "Hi", async (sender, arg) =>
        {
            await MessageReceived(arg);
        });

And at another location I have

        MessagingCenter.Send<object, FCM.NETStandard.Models.Message>(this, "Hi", msg);

And I can see that the subscription is made, but when the send happens, the subscribed delegate is not executed (any longer).
Tried it with other messages and it just does not do anything. What could be the reason?

Thanks

Ben