I'll tell you what I told the other guy who asked this same question on here. The only time I've ever seen this problem, when it was not a ground wire failure or misconnection, is where there was problem with the amp. It must be a problem of the circuit board of the amp not making a connection to the ground terminal of the exterior of the amp. Or more specificly, it could be a problem with the ground circuitry on amp's circuit board. The case that I saw this happen was the on the printed circuit board, there was a break of printed ground that would not connect the exterior ground terminal to the internals of the amp because of that break. The solution, although temporary, was reconnecting the break with well placed solder joints onto the circuit board. I did instruct the owner that he this is only a temporary fix and that he should get a new amp as soon as he could afford one.
And the possible reason why you are not getting one set of RCAs to allow the amp to turn on is the fact that it may have broken the ground wire in the RCA because of too much current being ran through it.
So all things considered, get a new amp and new RCAs.