Unable to update iPhone 8 Plus to iOS 17

That is because your iPhone is not capable of running iOS 17 or higher. Your iPhone 8 Plus is at the end of the road for the latest iOS software updates and cannot be updated past iOS 16.7.10. iOS 17 is supported on iPhone XR or later, and so is the latest iOS 18.

Cjmoore57 wrote:

Phone 8 plus won’t update to 17

That's correct. An iPhone 8 model cannot be updated past iOS 16.7.10. It lacks the hardware required to run anything higher.

iOS 17 is no longer available but iOS 17 & 18 were/are compatible with iPhone XR and newer.

That is correct. An iPhone 8 Plus can only update as far as the latest release of iOS 16 – currently iOS 16.7.10. It cannot, and will never be able to, update to iOS 17 or higher.

If you need something newer than iOS 16, you will need to purchase a new iPhone, preferably one that is likely to have years of updates ahead of it, like an iPhone 15-series or 16-series phones. (Of the iPhones that Apple sells new, only the 16-series phones support Apple Intelligence.)

IOS 17 is only compatible with iPhone newer than iPhone 8 Plus