When user is in home, he basically is logged in to his computer with cached credentials and can't change his password until he connects to domain. In order to change password remotely and force replacement of cached credential user needs co connect via VPN and when he is connected  to press on ctrl-alt-delete and press on change password. After password is changed he needs to lock the computer by pressing ctrl-alt-delete and then unlock it with "new" password. That should replace cached credentials. Read more