Q: I cannot activate iphone 5 after updating iOS

Have you purchased second hand device or you are the original owner?

If yes you need to contact the seller and ask him to remove this iPhone from his list of devices. Otherwise, your iPhone will be a useless brick.

Find My iPhone Activation Lock: Removing a device from a previous owner’s account - Apple Support

Apple seems to be having trouble with their activation servers. If you continue to get that message when it’s been resolved, you need to use the Apple ID it’s locked to, or if you’re its original owner, take it and its purchase receipt to a physical Apple Store or otherwise contact Apple.

(140914)

I have the same problem, I am the original owner and I have my iCloud account working on my computer (mac) and previously on my iphone with out a problem, now that I update my iPhone 5s to the new iOS 9.3 ask me for my iCloud account, and says the same thing "Incorrect Apple ID,  cannot  be used to unlock this iPhone. Funny thing that the clue that gives you is the same one I am trying, and the account knows that is the correct one because when I try random passwords and other emails it says "incorrect" and when I put the correct account and password just say "Incorrect Apple ID"... Thank you!

Hi Dear,

i've exactly same problem, I'am sure that am using correct original apple ID even i got the hint represented by my first letter from my email account in the ID request, I got tiried from this problem and this is last time I'll update my IPhone to new IOS software

P.S the suggested link didn't help me also and it seems that there's problem  in Apple new software because last two days a read many time same story in apple discussions.

I still have the same problem, I call to iPhone support and the advice to restore my iPhone but when it starts again still ask me for my iCloud account, and same problem, I have done so many things, I removed from find my iphone, removed from my icloud, and still can't do anything ... Please help!!!

See the new article from Apple on this:

If you can't activate your iPhone, iPad, or iPod touch after installing iOS 9.3 - Apple Support

thanks i'am trying but what meant by "under line in below"

Confirm that your device is listed in the My Devices section. If you don’t see it listed, check all your accounts.

Your device should appear under the My Devices section if you have one Apple ID. If you have more than one you would have to check you other accounts.

I checked and no device found but yesterday as one of recommendation i read i deleted my device from find Iphone department.

I am sure i don't have another account and I am the original owner of my Iphone

Thanks for ur response