Lack of notifications on iOS

When my friend sends me a message with Jami on his iphone (iphone XR, running latest iOS version), I immediately have a notification on Jami running on my phone running LineageOS.

When I send him a message, he is not notified. If he opens Jami, he is notified of my message only after sending me another message first. So I can’t reach him.

Is there some settings to be done so that he can be notified when I send him a message?