Periodically, felt hats can become misshapen. In order to get your felt hat back up to snuff, you can use the wonderful power of steam!
Turn on your tea kettle and create some steam. Don't soak the brim with this steam, but rather carefully expose the turned up brim to the steam. It should soften somewhat. Then train your brim to the result that you are looking for. Go back and forth between steaming and training. The hat should eventually "remember" the way it was originally blocked.