Can’t sign in to Apple Intelligence on iPhone 17 Pro Max (Australian model)

I purchased an Australian version of the iPhone 17 Pro Max, and I am currently located in Australia.

I have already changed my App Store region to Australia and successfully registered for ChatGPT.

However, when I go to Settings → Apple Intelligence and try to sign in, it shows an error message:

“There was a problem signing in to your account.”

I’ve checked my network and Apple ID settings, but the issue persists.

Could this be related to regional availability or account settings?

Any advice on how to fix this would be appreciated.

Thank you! 🙏