Once you're screen is back, it's worth running Disk Utility to repair any errors (Image credit: Apple / Future) If you definitely have power, but your MacBook isn't starting up, make sure it's disconnected from anything other than your charging cable and adapter.

Peripheral devices like printers, keyboards, external drives, mice and trackpads can all cause potential start up problems. Hit F2 or use the control bar to try increasing the brightness on your MacBook Pro. It’s also possible that you (or your cat) might have unintentionally hit the brightness keys on the keyboard at some point at that you screen is simply dimmed. Check the power indicator light shows so you can rule out a faulty power cable. If you're running on battery, connect your laptop to its charger just in case the battery has run down. It can be a massive relief to discover the issue is something as simple as this. This might seem obvious and you've probably already done it, but just to be sure, do check the power and brightness controls.

How to clear macbook pro hard drive