Infinity Basslink not producing any sound. Green light on.

I don't recall if it was before or after i had pep boys replaced my old car battery. in any case my Infinity Basslink is not producing any sound. So I got some advice from this site and others. I did check the amp on the subwoofer & it's fine. Also green light is on when I turn the car on. I also checked the other amp that powers the audio speakers and its' amps are ok. the only thing i did not check is that tube (fuse) that connects the wires near the car battery. is this the case, is that fuse blown? Can you advise if that is the case, and have steps to replace it. I'm not a audio techie at all -- i had someone install the car audio to my subaru impreza 2005. Thanks a lot.