Yikes
My biggest complaint about Behringer boards is that they always seem to break down, I hope that this isn't the case with your board.
Just a couple of obvious things to check, are you sure you are plugged into the 'line in' and not the 'insert'?
If there is a 'Mic/Line' switch push it a few times to make sure it isn't stuck in the down position.
If you are hearing sound but not seeing a reading on the meters the SOLO circuit, meter bridge or connector cable may be defective, but the channel may still work.
Check all the channels with the same sound source and cable to be sure that it isn't a cable problem.
My advice to you would be:
1/ Never replace a Mackie with a Behringer
2/ Kick the ass of whoever sold you the board if it is in fact defective.
3/ Try to get the seller to pay for the repairs.
4/ Kick their ass again just for the hell of it.
I hope you can get things sorted out. Good Luck