Monitor XT12 Subwoofer issue

I just received my new subwoofer and it powers up but no sound. I have tried RCA cable and speaker level setup as well. Speaker level power up the speakers fine, but still no sound from the subwoofer. I hate to return it because it's heavy and don't have time as well. I was too excited about it, but now I have to deal with the issue. Any idea how to fix it?

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