What happens when you just tap the button for a quarter second?
Does a menu pop up to change the backlight, etc?
Is it a new problem?
Have you updated the unit?
Even if it’s a new problem on the same version of software, bugs can pop up on their own.
Don’t bother calling HB if your unit isn’t running the latest version. That’s what they’ll have you do first no matter what.
The button physically works (since you can power it on), so it’s definitely a software issue and should be an easy fix on your own.