Surround channel speakers are not working

surround channel speakers are not working. front speakers work, no center speaker connection, but I hooked up a small pair of speakers to the surround channel, one cable is 50 feet long and the other 30, both are 16 gauge wire. speakers are functional, I hooked them up to the front channel and they work, but for some reason nothing is shooting out from surround connection.

thanks

Yamaha Natural Sound AV Receiver HTR 6130