HALP! Sub isn't working after paying to have it fixed

Hey all, so I'm new here and am trying to find a solution to why my sub isn't working. So here's what happened; my fuse holder/fuse on the wiring running to the battery kept loosening up for whatever reason. I jimmy-rigged it many a times with electrical tape and cut back the wire more thinking maybe it didn't have enough contact with the fuse holder. This worked basically every time I did it until just recently. So wanting my loud music back I went to Best Buy today hoping that they could just put a whole new fuse holder on the wire fixing the sub for good. The guy said it would cost 40 bucks to fix it, which I thought would be worth it since I figured that was the only problem.

So after he finished up I get in my car and actually hear my sub for the first time in a while. Then before I even get out of the parking lot it stops working again.. I turn around and go talk to the guy that "fixed" it and he explains that it could be the sub itself, amp, or other wiring going to the deck. So I take my deck out, check all the wires (which are all connected and seem to be good) and strip and redo the wire connecting from the back of the deck to the amp.

Now my amp won't even turn on and I'm not sure why. So my question is, is there anyway to check to see if the amp or sub is completely dead? What else could be the problem? Don't know much about car audio myself, just the basic stuff like how to install a deck/speakers, so I figured I could ask the experts online. I really don't want to have to spend anymore money to have a shop see what they can do, as I feel like I basically threw away the $40 I paid Best Buy. I even bought new Polk Audio speaks for my front doors while I was there but it's just not the same without my sub!

Anyway, any help would be greatly appreciated and I look forward to seeing what you guys have to say! Thanks for looking