My central speaker is not working. It seems to be a subwoofer link problem tho. What to do?

[Nature Guardian]

Whatever speaker I put as the center speaker, it won't work. The audio would be barely audible. It seems to be a problem with the subwoofer, and.... I've tried everything but have no idea if there's to way to save this. :/

 

[gorfias]

Sub woofer typically different channel from center speaker.

What is it plugged into (my sister has an old bose system and everything feeds into the subwoofer so, the odd set up does occur here and there.