Did I blow my amp?

So basically I have a 2000 VW golf, I bought it used with wiring and amp etc, one of the issues with the car is battery drains so when I bark I take one terminal off so it isn’t draining. So in the car was a sub and amp I had a friend hook it up cuz I couldn’t figure out what I did wrong it was working great I ended up parking my car turned it off and took battery terminal off got done doing what I was doing. Hooked battery back up but now my sub won’t work even tho it just was? Any ideas what I mighta done? Or trouble shooting thanks.