Disconnected and reconnected PSU. Nothing.
Discussion
Pulled out memory tried booting without them. Nothing. Reinstalled them. Nothing.
Integrated graphics, or separate card?
Integrated graphics.
https://www.gigabyte.com/Motherboard/A620I-AX-rev-10#kf
Going to try a different power supply, and if that don't work, contact customer support.
Tried a different PSU. Still nothing. Went through Gigabyte's long online questioning, and then finally submitted my problem. Will see how it goes.