Onkyo TX-SR703 surround sound issue

greetings .....my long-performing-perfectly TX series receiver amp has posed a new problem to me in our theater room that I cannot resolve: only 2 of the 7 channels play when I use All Channel Stereo ......yet, when I "test tone" all 7 channels, they all test tone perfectly so that tells me no issue with signal getting to each channel (at least when tone testing) .......the 2 channels I do get sound out of are the Center and the Left main ......????? .......also, it does not matter what listening mode I select, I do not get sound from all channels, I just used the All Channel Stereo as example, as it's my listening mode for my docked iPod ......any assist would be greatly appreciated......(note: I was going to crawl under house to inspect condition of wires that are run under hard wood floor, but if all 7 channels are tone testing a-ok, there is no need to do that, speaker wire runs would have to be sound if each channel tone tests a-ok)