I actually JUST fixed it, pop it out of the wristbands and kinda pull out the bottom right button...or make sure there's not something inside the wristband on that button. Mine has been going off constantly for the last 24 hours and i just pulled on that button with my nail a little bit and now its gone!
I have this very same problem. Mine is about 2 years old before it started. When I take out out of the band assembly it stops giving me the constant notification message. The clearances are very close for the button to work properly so just a little dirt will cause the issue ( continuous button pushing indication). Dropping the watch and it hitting on just the right spot can also cause this clearance problem. I've cleaned everything good and yes it was nasty and so far so good. To troubleshoot take out the watch module from the band and see if anything changes. Then you'll know to go after the band or watch. A new one may also do this if it was dropped anytime at the factory or in route to you. The quality assurance at the factory seems to be going down as time goes by, sorry fitbit but that's the truth.