1.  It is possible to install the battery upside down in the Voicebud.  If you this the Voicebud will not power on.  It isn't easy to do you have to force the battery door closed, luckily it doesn't seem to damage the Voicebud.  
  2.  Earwax in the tube could lower the volume enough that you think the Voicebud isn't turning on.  
  3.  This is extremely rare, but I have found a couple brand new batteries that did not work.  If the Voicebud isn't turning on the first things you should try is installing a brand new battery.  
  4.  Tap the button on the rocker switch without the nub 10 times and as it gets louder you will hear beeping noises.  If you do not hear beeping take off the dome and see if you hear the beeping when you tap that button. 
  5.  If you do, then change the dome and your device will work.  If you do not hear anything when you remove the dome and tap the button try a fresh battery and make sure to leave that fresh battery out 5 minutes before you begin to use it.  I believe you will have success at this point.