NC Talk at Hetzner does not send push notifications to iOS

I have a NC at Hetzner

I’m using the Talk app with it on iOS and it works. Except I don’t get notification about new messages on the phone.

Why? Is it a limitation of NC, NC Talk, the NC Talk iOS app, Hetzner’s hosting, or a config problem?

Well don’t you think. you should ask this question Hetzner?