Unable to participate in family sharing

Hey everyone, I’m having trouble participating in family sharing.

Supposedly the organiser's iPhone 13 mini and my iPhone SE (2nd gen) are connected via family sharing. We can see each other’s names etc in the settings (cf. screenshot).

But if I try to check out my subscriptions (Apple One should appear here) or if I want to just use Apple Music - it sends me straight back to “start your free trial” and asks me to buy a subscription.

Things I’ve tried so far:

-Log out both devices from iCloud and log in again.

- Update Software to latest version.

- Restart devices.

- Exit family and rejoin family sharing with new link.

- Verify the Apple ID of both devices.

- Contacted Apple support hotline.

Important info:

The organiser’s device is registered in 🇦🇹 while my device is registered in 🇩🇪.

Could that be the problem?

Thanks for any suggestions 🥲