On your iphone 15 if you are trying to get apple intelligence after updating your iPhone 15 to the latest iOS 18 version and apple intelligence is not showing or not working then you need to check with Apple intelligence supported models.
Apple Intelligence is Not Supported on iPhone 15 Mobiles
If your iphone is iPhone 15 mobile then it won’t support apple intelligence and it wont work. Apple Intelligence only works on iPhone 15 Pro mobiles and iPhone 16 series only.
And Presently Apple intelligence only supports A17 and A18 bionic chips only and also it works on limited countries only.
What to Do if iPhone Apple Intelligence is not working or not supported on iPhone 15 models of iPhone
If you are very eager and want to use apple intelligence features then you need to try to exchange your iphone 15 and get the latest iPhone 16 series and this is the only way you can get apple intelligence.
Why Does Apple Intelligence not Work on iPhone 15?
Apple released Apple intelligence only for latest models of iPhones, because A17 and A18 are the fastest chipsets of iphone and if apple releases for lower models then it will be an issue, all iphone previous model chipset models will be complaining more and it will be slow and it will have issue when using apple intelligence on iphone 15 series.
Which Models of iPhone supports Apple intelligence
Apple intelligence works on only the iphone 15 Pro series with A17 bionic chip and iphone 16 series A18 bionic chips.
Is Apple Intelligence only on iPhone 16?
No! Apple intelligence works on iPhone 15 Pro series and iphone 16 all series (A17 and a18 Bionic chips only) it works on iPadOS with the latest version and Mac M1, m2, m3, m4.