Still not working? Now it is time to get on the phone or get in the car. Call Applecare or visit your local Apple Store or local Apple Authorized service provider. If your machine is under warranty examining the computer and repairing it should be free. You might even end up with a new computer- depending on what is wrong with it.
If your machine is not under warranty make sure you get an estimate. You’ll have to be the judge and determine if the repair costs are worth it versus purchasing a new computer. Keep in mind that some places will charge you a fee just to look at the computer (in my experience, this has been at least $90). Sometimes the fee goes towards repair, sometimes it does not. Check first.
I have found if you take it into an Apple Store Genius Bar the techs will try to help you without having to check it in and charge you. If you are out of warranty be sure you ask if you are getting charged for an evaluation.
Hopefully, one of the steps above will get your computer up and running. Good Luck!