Hi, I am using iphone 6 plus. My device is ios 12. I can’t found any notification about upgrade my iOS version. Can you help me please to update my iOS at least 14.

iPhone 6 Plus can’t update with any version of iOS higher than 12.5.5. I

Your iPhone "6 plus" hardware is limited to using iOS 12.5.5. Please refer to iOS 15 and iPadOS 15 are compatible with these devices which lists iPhones compatible with newer software.

Your 8 year old iPhone 6 hardware is not compatible with any version of iOS higher than 12.5.5. If you need a later version you will have to buy a newer phone.

iOs 12.5.x is the best that you can do with the iPhone 6 Plus. It cannot be updated any further.

I’m responding to upgrading to 15 from 12 iOS. I have iPhone 7. It shows that it’s available but won’t upload it. It seems there could be a connection to wifi even with it on. Backup and this post that 15 is ready. Ahhh

To update over the air from the phone all of these requirements must be met:

• You need at least 6 GB of free storage
• You must be connected to a Wi-Fi network (and not a personal hotspot)
• The phone must be charged to at least 50%, and preferably plugged in so it stays above 50% during the update
• The phone must not be in Low Power Mode
• The phone must not be connected through VPN, and it may be necessary to delete any VPN apps and VPN profiles
• The phone cannot be in Airplane mode
• You cannot still have a beta version installed on the phone
• You cannot have a previous version that was downloaded, but not installed - go to Settings/General/iPhone Storage to look; if you find an iOS installer, delete it

If you can't meet all of them you can still update using your computer.