Fidownftw1

Okay so I recently bought me an fi sp4 and a sundown scv 2000 my setup consist of a big 3 extra battery Shca rcas toolmaker bat terminals all that good stuff with all 2/0 ofc wire it has worked great for a couple weeks now but the other day I went to build a box for my battery and unhooked my amp and battery and ever since then my amp will turn on but my sub won't work I've tried everything from other rcas to rerunning all my 8 guage speaker wire relocated my amp and all that stuff now what's confuses me is that earlier today I had the sub out and tested it outside the box and it worked but right when I put it back in the box it quit working . This is really stressing me out any suggestions???