|"at my knowledge if the voltage is good then the amp is good as well"|
If your PSU is only capable of delivering 12V @ 2A (due to some sort of internal failure) & your system needs at least 12V @ 20A, the system will not boot. Using a mutimeter will show the voltage to be within spec. Unfortunately, there is no simple home method for checking amperage & the test equipment costs thousands of dollars. I'm not 100% sure the PSU is the problem, but that's what I'd be looking into if it was my system. Of course, if it was my system, I would have posted the complete system & PSU specs to make it easier for people to help, but that's just me.