How can I update my iPhone 6s

One thing that you should know and confirm and that is whether you have an iPhone 6s or do you have an iPhone 6 (Without the S) This is important because an iPhone 6 can only be updated up to iOS 12.5.5 and NOTHING HIGHER. You need an iPhone 6s to update higher than that to iOS 14/15. Double check which iPhone you have.

Open Settings ➔ General ➔ About ➔ Model Name: What does it state there?

Axel F.

There is your answer. Your iPhone model is NOT an S model. It is an iPhone 6 Plus and cannot be updated past iOS 12.5.5. A newer iPhone model is needed to update past that iOS version.

Axel F.