I just changed the battery in my Hampton Bay ceiling fan and now the remote doesn't work, does it need to be reprogrammed?

They don't have memory. Verify good batteries and oriented correctly.
Usually DIP switch. As long as they haven't been changed should be OK.
If they were, would have to look at receiver in fan switch settings, and match.

Are you sure your replacement battery is good? Did a wire get pulled out?

Ceiling fan remote controls - help and FAQ- Ceiling Fans N More (http://www.ceiling-fans-n-more.com/ceiling-fan-remote-controls.php)