The terms and condition say that the offer must be redeemed within the first 90 days (~3 months). So to redeem now, the purchase registering must have been after 2023-11-23.
Apple TV+ offer - Terms and conditions - Apple
Apple TV+ offer - Apple
… with the purchase of a phone …
More precise: to new subscribers, with the purchase of a new iPhone (or select other devices) from Apple or from an Apple authorized reseller (not John Doe on the street corner). One offer per user, or family (in case of Family Sharing). That excludes current subscribers, and previous subscribers that have had their extended trial.
Apple TV+ offer - Terms and conditions - Apple
The offer is for the first registered user of that new eligible Apple device. I.e. not for the buyer, in case of a gift.
There are no known reports from users that got exceptions in the last few years. It seems that the staff have been instructed to be strict about the 90 days.
Users do report getting reminders in Settings and email messages from Apple (last week of the 90 days) about not waiting too long to redeem. For this to work, Apple needs to know your Apple ID as contact for this purchase, and you have to not block such emails from Apple.
If you feel that you meet the conditions and you should be eligible:
Read here if you have trouble redeeming: If you can't redeem your promotion for an Apple subscription - Apple Support
↳ Step 5 says to contact Apple if the prior steps didn’t bring a solution. They can assist.