My wife's Macbook Pro suddenly dropped to a black screen with the power still on; keys light up, caps lock light comes on; display is clearly getting power. Holding down the power button kills power to the machine, but it does not restart. If I hold the power button, I get the "power connected" sound you get when the AC Adapter is plugged in, but nothing else - it goes right back to the black screen.
I've tried resetting the SMC and the PRAM/NVRAM with no success. Also tried plugging in an external display - nothing. What are my next steps? If it helps, we have another Macbook running Catalina I can use for any sort of boot disks or something.