Q: Just upgraded iPhone 5c to 9.3 and upon reboot after putting in my lock code screen says this iphone is linked to an apple id

I have a friend who just upgraded her iPhone 5c to iOS 9.3.  Upon rebooting and entering her lock code, the screen now says the following:

Activate iPhone

This iPhone is linked to an Apple ID. Enter the Apple ID and password that were used to set up this iPhone. (l*****@s*****.com)

I've never seen an iPhone display this in all the iPhones I have updated.

If she logs into icloud.com using the email address at the end of the message above, and runs the Find my iPhone app, it shows her iphone as being offline so we know that it is linked to the email address she logged into icloud.com with but when we use that email address and the password that logged into icloud.com successfully, the phone says the credentials are not correct.

How can this be if she can log into icloud.com and see the phone is attached to this Apple ID?  How is it that the phone wont accept the credentials as being correct?

Anyone run into this before.

And before anyone asks, she purchased the phone directly from Apple several years ago and has been the only owner of the phone.

Any thoughts greatly appreciated.

Dan