Screen Black, not connecting

I was at work with my fully charged gear fit when I noticed it was acting odd (showing the battery level every time I got a notification) shortly after it started that it went black and would not show anything, I tried rebooting it and when I hold the power button it simply vibraates then nothing happens.I've tried turing off blue tooth on my phone, made sure it wasn't still somehow connected, held the power button for 10 seconds then 20 seconds (all it did was vibrate like when you plug it in). HELP