How do I turn my Mac on
My Mac is not booting. A circle with a line passing through shows
MacBook Pro 13″, macOS 10.13
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You might have to reinstall macOS, check the steps in this article to use Disk Utility to check your drive for possible errors and let it fix those:
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A prohibitory symbol, which looks like a circle with a line or slash through it, means that your startup disk contains a Mac operating system, but it's not a version or build of macOS that your Mac can use.
- Press and hold the power button on your Mac for up to 10 seconds, until your Mac turns off.
- Use Disk Utility to repair your startup disk.
- If Disk Utility found no errors or repaired all errors, reinstall macOS.
- If you still need help, please contact Apple Support.
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copied from: If your Mac starts up to a circle with a line through it - Apple Support