Contribution d'origine par : James Mitchell ,
Has anything happened to the machine that would cause this? Any water damage? Have you tried a [https://support.apple.com/en-gb/HT204063|SMC and PRAM] reset? Where was the Mac purchased? If it is in the EU, you might be eligible to claim under EU consumer law for a repair as long as the machine is in good condition. You can do this through either Apple or any AASP.