Why does activation locked iphone want a password that was reset?

I have an Iphone which is activation locked. I received this phone from our HR department that was used by an employee no longer with the company. We were able to get his apple id from the device and have since reset the password to gain access to the account but phone is not listed in attached devices nor find my iphone. The question I have is why won't the current password for the apple id get us pass this activation lock when it works to get into the apple id itself?

Thanks in advance for the help.