i dont know if to remove the cable right now, because if it is finally charging, i dont want to stop it and mess it up again.
so what now?
edit: i didn't disconnected the cable yet. but the Red LED turned off.
You are charging from the electrical outlet, are you?
Just let it charge for at least two hours, it is a good sign that the LED went on.
Furthermore this red LED also known as 'red light of death' is a common issue of Nexus devices. It's an indicator for the batterie not to charge or because there was a thermal shutdown cause by too much heat and you only can solve this by screw off your device.
I hope you dont must go this far. Just be patient and wait what happens after the charging period.
Did you also try to charge it with another cable? Try again to press down volume down key and plug in the cable.
By 'not charging at all' do you mean, there isnt this batterie logo when charging?
Edit: Try this volume-down-plug-in-cable a couple of time. It may not work the first time you do it.