Hey ive got a sub problem i just bought brand new 2 boston g2s and a alpine mrp-m650 im running my subs at 4 ohms. I just got it proffesionally installed and i was listenin to a loud song and my left sub completely stopped working...any ideas??

 

Just a guess, but i'd bet a wire (quick disconnect) fell off the wire or came off the connector.
And that might be inside the box.

Take it back to your professional installer and let them fix it for free.