Will not start, security light flashing

I went to go start my car this morning, and it cranked and then shut off. I went to turn the car on, and now the car won't even turn on, no lights, no nothing, no radio, just a security light flashing, and the car noise that accept goes off when your door is open so. I went to go charge the battery and the guy said the battery needs to replace. so I replaced the battery and the car still won't start. Ehh. It won't even crank radio won't turn on, windows won't roll down, security lights still flashing. my remote on my car control will not work; lock, unlocked, panic trunk button, nothing. I've tried everything. checked all the fuses. everything works fine I'm at a loss. please help.