Could be me, but "some sort of green light" sounds rather vague. Care to elaborate?
Have you got any external circuitry attached? What are you suing to power the photon now? Does the reset button do anything? Is safe mode possible? If DFU mode possible? Does the device get hot?
The 5V source was one that plugs onto the end of the breadboard and you just hook up a power supply. I made tests before to ensure voltage and amperage were within limits. It was.
The “green light” was the indicator light, dimly lit, It wouldnt do anything other than that.
Ive tried to go back to using USB and nothing except the dim light on D7 works.
The quality of a power supply has more factors than just voltage and amperage but also how good the DC is filtered.
Standard 5V chargers often only use a bridge rectifier with hardly any filtering (if any at all). If you used one of these without additional filters you might have damaged the regulator.