The HR person might have changed jobs / companies. It sounds like this is more an internal screw-up on their part, and that they would be lucky to have you. De

The HR person might have changed jobs / companies. It sounds like this is more an internal screw-up on their part, and that they would be lucky to have you. Definitely email the head of HR. In the email, try and go with "really enjoyed interviewing, but why haven't I heard back, as it's been 4 weeks?" instead of an angry message. I doubt they turned you down; rather, they aren't very well coordinated.