Why can't I update my iPhone 7 Plus to iOS 16?

The iPhone 7 Plus originally ran iOS 10. It received five major iOS updates, but has reached the end of the line. It cannot run, and will never be able to run, iOS 16 or higher.

If you need something more recent, it is time to purchase a new iPhone, preferably a 15- or 16-series phone that can run iOS 18, and is likely to have years of future updates ahead of it.

joren34 wrote:

How to fix iPhone 7 plus cannot update my iOS 16 please help me

That's correct. iPhone 7 cannot be updated past iOS 15.8.4. It is too old and lacks the hardware required to update further. If you need a higher version iOS, then you need to retire you very old iPhone at this point and a new iPhone.