iPhone 5 won't show iOS11 update I'm trying to update my iPhone 5 from iOS 10.3.3 to iOS 11. But when I try to find the update, my phone tells me 


I tried iTunes too and it's behaving the same way. It's like I do have the latest version of iOS but I know it's not true. 

I tried turning my phone off and on but no joy. 

I haven't done a full restore yet because I'm trying to avoid that.  I have backed up my phone on my computer using iTunes, though. 

Any troubleshooting suggestions?
Only the iPhone 5S model and newer can be updated to iOS 11. The 5 cannot run iOS 11.