I have an 08’ macbook pro 15”. The last time I used it it worked good but needed to be plugged in because battery was on its last legs. However, I recently tried to power it on using the 85w power cable and haven’t been able to get it on. I tried trackpad, space and power as well as cntrl shift alt power and power on while removing and reinstating charger. None of these have worked. Would It be worth it for me to buy a new battery or is there a more serious problem here?