Half stack guitar amp problems.?

I bought a half stack from a local music shop's going out of business sale. When i purchased the amp the 2 right speakers did not work. i didnt have a problem with it since i was just starting out. Now i have a band and the 2 speakers not working is a problem because all the other instruments are drowning my guitar out. My friend and i have tried to rewire them and also put a new speaker in and that was no help. What could be causing this?