cannot activate my ipad after upgrade to iSO 9.3

after upgrade to iSO 9.3 i tried to use my apple ID and password (Im sure it is right) to activate the i Pad, but i got a massage of incorrect apple id and this user name cannot be used to unlock this ipad. however this apple ID is the only one used on this Ipad scene i bought it. please help what should i do?

Thanks,