Diagnosis
The control panel has locked up or the main control board is malfunctioning. A soft reset almost always fixes this.
How to Fix It
Unplug the fan from the wall outlet. Wait 60 seconds. Plug it back in. The fan should power on in its default state and all buttons should respond normally.
If That Didn't Work
The internal wire harness connecting the control panel to the main board might be loose. You'd need to remove the rear grille (a few screws) and check the white connector near the top of the fan housing—push it in firmly to reseat it.
Heads Up
Don't just turn it off with the remote or front button; a full power cycle from the wall is required to clear the electronic glitch.