Why won't my Galaxy S7 turn on?

[AC Question]

My battery completely ran out, and then I went to charge it. There was a loop of the battery with a charging icon, and the phone turning back off. When it booted to that icon, there would be a brief vibration. I tried booting with the volume keys and the power button, and that worked at first; it booted to the "do you want to use a custom ROM?" screen, so I pressed cancel to reboot the phone. After that, the phone turned off, and the notification light started to fade between blue and cyan. It just repeats that now, and none of the buttons will boot the phone or do anything.

 

[zledzhydro]

you got a bricked phone, try searching on how to unbrick your phone, go to XDA forum they might be able to help you

 

[B. Diddy]

Welcome to Android Central! How long have you tried charging it on a wall outlet, undisturbed? Let it charge overnight, then try powering on by pressing and holding Power for at least 10-15 seconds.

Also, is the phone rooted?