Active directory 2012 password policy

I have a windows server 2012 R2 active directory environment running in my office. I have a primary domain and a child domain. Both the domains have password complexity enabled. Active directory admins are able to change the password for the users. When users try to change passwords on there laptop using ctrl+alt+del they get a password complexity error. More over, when I tried to change the password on my laptop, it let me change the password once, then it stopped working all of a sudden. please advise what might be the issue