iPhone Activation issue

I have iPhone 6 and I reinstalled the software to latest version by using PC. Now, when I turned the phone ON it asked for to enter iCloud to activate this phone. This iPhone is linked with an Apple ID u****@icloud.com.

when I enter the same ICloud ID and Password. It says that this ID is not linked with this phone. Even I’m sure I was used this ID and password to activate this phone before.

whats the issue?