I just had what may be a similar problem. I was using the laptop, set it aside and presume it either went to sleep or hibernated. But it would not turn on with the power button and plugging in the AC did not get a charging light. Dead.
Reading forum posts I concluded I needed to either disconnect the battery or the CMOS battery. Alas, I did both so I can’t say which worked. But when I plugged the main battery back in I had lights (!) and it booted find with 61% battery left.
My only other note is that, when I had noticed it lost battery slowly when completely shut down for a month I modified the BIOS to disconnect the battery. This may or may not have been a factor in my recent event but I turned that setting to NO for now.
I think, but don’t know, that setting means the laptop won’t boot on battery because, duh, it’s disconnected. If that’s the case (I may try testing) then the setting is only for long term storage, imho.
Anyway, no biggie to reset the CMOS if that’s all it takes but I’m leaving disconnect set to NO for now.