I have an L580 that will not boot up (2 years old and out of warranty). The caps lock and power button flash, but that's it. This same laptop was not holding a charge a couple of weeks ago, and I replaced the battery. It worked for two weeks. Now nothing. I suspected the battery and took it out, plugged the laptop in and tried to power it on, same thing. Power light and caps lock blink. Tried adding a monitor and keyboard, no difference. Tried F12, Function + F2, Windows key, nothing changes.

Hello Allied1,

Welcome to Lenovo Community

I'm sorry to read that you're having issues powering on your ThinkPad L580.
Kindly try to unplug the AC adapter, then remove the battery, press and hold the Power button for around 20-30 seconds.
Once done, reconnect the battery, plug in the AC adapter and let it charge for a couple of hours before turning it on.
Update us how it goes.

Regards, 
Lorenzo_Lenovo

Thanks for the reply. Removing battery, holding power button for 30 seconds, and replacing battery didn't change anything. I've tried it with the new battery and the original battery. I also tried it with the battery removed. Just flashes.