Question Motherboard won't boot

Hello,

I have an old computer that worked fine before 6 months in storage.
I went to boot it back up and I get nothing, I checked the PSU and the fan spins when jumped. The motherboard has a green light when it's getting power, but it does nothing when trying to boot. No beeps, no fans, nothing. I tried disconnecting everything and reconnecting, no change. Tried booting with no RAM, no beeps. I also tried a different I/O cable for the power switch. I tried removing the battery and attempting power cycle, then reinserting battery... no change. I also tried another PSU, no change.

Any ideas? Anything else I can try before assuming it's a bad motherboard?