Chosen Solution
I have a late 2011 macbook pro which I haven’t used in a few months. I plugged the charger in and the light is green however it still won’t turn on. I checked the battery charge status by pressing the button on the side and all 8 lights blink 5 times. Any ideas?
When battery goes unused for months best practice would be to charge it to 70/80% and disconnect it from the system. You may have a battery gone bad there, despite it still holds charge. Try disconnecting it from the logic board and plug in the magsafe, if the board is still alive it should start on its own.
