How do I fix unavailable ChatGPT integration on MacBook Air M3 and iPhone 16 Pro?

Are you in country, where ChatGPT should e available?

See: Get started with Apple Intelligence on iPhone - Apple Support (AM)

• Availability: Apple Intelligence is available with Siri and device language set to English in most regions around the world. Apple Intelligence is not available on iPhone and iPad if you’re in the EU and if your Apple Account country or region is also in the EU. For more information, see the Apple Support article Apple Intelligence requirements.

Use ChatGPT with Apple Intelligence on iPhone - Apple Support (AM)

Note: The ChatGPT extension is available with Apple Intelligence** in iOS 18.2 or later on all iPhone 16 models, iPhone 15 Pro, and iPhone 15 Pro Max. Apple Intelligence is not available on iPhone and iPad if you’re in the EU and if your Apple Account country or region is also in the EU. To check whether Apple Intelligence is available for your device and language, see the Apple Support article Apple Intelligence requirements. You must be at least 13 years old or the minimum age required in your country to consent to use ChatGPT. For more information, see OpenAI Terms of Use.