why i cannot update my i phone 6s plus to 15.5 ios

Are you sure you have a 6S plus and not a 6 plus?

Go to Settings > General > About and look at the model number.

• If you have an iPhone 5S or 6/6plus, the highest you can update to is 12.5.5

• If you have an iPhone 6S through 13, you can update to 15.5

What happens when you try?

Can you post a screenshot of the whole screen, it could reveal why you aren't able to update.

Make sure you:

• Are using a WiFi connection (not a hotspot).

• You have an active cell signal (You need both WiFi and cellular service to perform the upgrade).

• Have your battery charged at least 50%. Better yet, keep it plugged in during the update.

• Are not using a VPN connection.

• Do not have power save mode turned on.

• Do not have a beta version installed.

• You have at least 6 gigs of storage available.

You can also check out this article for help -

If your iPhone, iPad or iPod touch won’t update

If your iPhone, iPad or iPod touch won't update – Apple Support (UK)

on here it says it can only be updated to 12.5

Not sure what "on here" is referring to. Please take a look at this Apple Support document and you will see that the 6s Plus can definitely be updated to iOS 15.5. Seems pretty clear.

iPhone models compatible with iOS 15.5 - Apple Support

Hello ~ You misread the message as a 6s plus can in fact be updated to 15.5…*Kurtosis* correctly wrote ..

“If you have an iPhone 5S or 6/6plus, the highest you can update to is 12.5.5

If you have an iPhone 6S through 13, you can update to 15.5”

Take a look here:

iPhone models compatible with iOS 15.5 - Apple Support

~Katana-San~

Ummmmmm I have a 6s plus and it updated up to 15.5 but on here it says it can only be updated to 12.5 or smt I’m just confused and I am for sure that my phone is a 6s plus

Yes, the iPhone 6S can be updated to iOS 15.5. Many users confuse the iPhone 6 and 6S, and their respective iOS versions.