Gateway 300S Powers on completely BUT will not go into POST…

I have a “Gateway 300s” Desktop PC that when powered on, “all” the internal fans power up, —{ processor, power supply fans, internal tower fan, the H.D.D. spins up, etc…}—however, the PC does NOT enter into POST. Any help-(thoughts/ideas)- would be greatly appreciated…

Thanks so much…

PS: The “Power Button” on the front of the unit is Orange/Amber instead of Green also…(I have swapped out the P.S. with another known working one and the same issue occurs — an “orange/amber” light instead of green…)

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