I had the same issues and think it got a little wet from drizzling rain....
So I put it in a bag of rice for a bit and then on the cold setting of the hair dryer on the ear piece. Rebooted it and it works again. COLD setting on the hair dryer! So you don't fry anything internally.
Pushing on the top. Didn't work.
Blowing in the top. Didn't work.
The voice memo trick. Didn't work.
So for those of you out there that get through the suggested tricks above and it still didn't fix the problem. I hope mine help.
;)