Only LED #2 is lit?

Hi!

I’m working on a customer’s iMac 2019 for a no-power issue. She stated it was rarely used for the first year and a half she had it and just recently started using it for remote work. I can’t imagine that she could have done anything to it to cause an issue. She even had the original box, foam, dust cover, everything. One day, she went to turn it on, and nothing happened. No fans, no chime, just a bit of an initial whine from the PSU capacitors when it’s plugged in.

After checking the diagnostic LED’s on the logic board, *only* LED #2 is lit. LED 1 would indicate trickle power and LED 1 + LED 2 would indicate the system is on and receiving enough power. Never, though, have I only seen LED 2 on with LED 1 off. I checked the diagnostic guide for this iMac and nothing in the troubleshooting section says anything about an LED being on “out of sequence” of the prior prerequisite LED’s.

What I’ve tried so far:

• Different working power cable
• Different wall outlets (both at client’s location and mine)
• Checked power button cable
• PRAM battery OK @ 2.8V
• RTC clock reset (because why not, at this point.)

Any ideas?