why my iphone 13 pro max cant purchase the apple Care+ ?

When did you buy the phone? You have 60 days from the original date of sale to add AppleCare+.

CORRECTION to CORRECTION: I was reading the date US-style. My error.

Contact AppleCare+ support: Buy AppleCare+

Unless that's a European date format... 6 April instead of June 4th...

What is the model number in settings and what country are you in? AppleCare+ may not be available in all countries, and can only be purchased in the country where the phone was originally sold.

Yeah, and June 4 is in the future, so I corrected my post. Twice.