I can't redeem Apple Music 6 months free trial

That is a weird NON-offer.

I have a new iPhone, I have an Apple Music subsription so I don’t get the free six months music? What does Apple has in mind to keep this customer with subscription? Grrr.

See here: https://offers.applemusic.apple/en-au/six-month-offer-devices

Note that it’s for new subscribers only.