If the battery is low the phone will usually vibrate but not turn on.
Yes, 3.1V is very low considering that the true reading of a fully charged battery is usually above 4V.
Thanks Im gonna try to see if a new battery will solve my problem cause I tried hooking it to the charger and letting it set and im not getting anything and then I check the battery voltage again and noticed its dropped to 3.0v now.
If you're trying to charge the battery while it's in the phone.. You might :
Want to try a different cord.
Try different charger or usb port.
It can also be a bad phone Micro Usb /charging port.
Good luck