My mac won't start

What to do when your Mac shows only a gray screen or a Prohibitory sign (no left turn) at Startup:

1) First, use Disk Utility to Repair/First Aid your drive.

Since your Mac is not working normally, you can invoke Recovery Mode by holding Command-R at Startup.

Recovery Mode contains several useful functions, including a special version of Disk Utility that does not need the rest of MacOS to be running to do its job of repairing your disk.

"Regular" Recovery gets the Utilities from special partition on your normal boot drive. If you see a spinning globe, you have invoked (or fallen back to) Internet Recovery, and you see the Globe because it is fetching the Utilities from the Internet. This takes a little longer, so be patient.

About macOS Recovery - Apple Support

Once you get Disk Utility running, this article describes how to repair your disk:

Repair a disk using Disk Utility on Mac - Apple Support

Once Disk Utility reports your drive has been successfully repaired, you can try booting MacOS in the regular way. If that works, you have fixed the problems and you are done.

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If Disk Utility made some repairs, but there are still some problems remaining, you should run it again until your drive comes clean, or Disk Utility reports it cannot be repaired.

If disk Utility suggests you should ERASE your drive, that is a radical step -- this will delete all your files with no possible way of recovering them. Post back here for additional options before you do that.

Prohibitory symbol

When you see a circle with a slash symbol instead of the Apple logo, it means your Mac couldn't find a valid System Folder to start up from.

If you're using your Mac at a school or business, it might be trying to start from the wrong version of macOS. Contact your IT department for more help.

If this is your personal Mac, try reinstalling macOS using macOS recovery.

If you have already tried using ONLY Command and R, your Recovery partition may be damaged.

Restart and hold the Option key at the chime. Your Mac should light up a gray screen.

Over the course of the next several minutes, it should draw an Icon for each potentially-bootable Volume it can find. One may be named Recovery. If so, choose that one and tell it to proceed.

If you can't do an Internet Recovery then you will need a flash drive with the entire macOS DMG. You need access to another computer preferably a Mac to get this. This is the downside to no longer having an optical drive and retina Macs and iMacs not shipping with the original OS X/macOS install DVD.

Here's the direct link for Sierra: https://itunes.apple.com/us/app/macos-sierra/id1127487414?ls=1&mt=12

Mountain Lion sadly is not free, $20: OS X Mountain Lion - Apple

El Capitan: https://itunes.apple.com/app/os-x-el-capitan/id1147835434?mt=12

High Sierra: https://search.itunes.apple.com/WebObjects/MZContentLink.woa/wa/link?mt=11&path= mac%2fmacoshighsierra

You may be able to find DMGs outside of the Mac App Store but do so at your own risk! I'm sure there are several good copies on torrent sites.

P.S. Like was mentioned above, it's possibly that the WiFi performance is not good enough for an internet recovery especially if your device doesn't have 802.11ac and you aren't using a 5GHz router. Ethernet will help but you will need the thunderbolt to gigabit ethernet adapter for this. You can always make an appointment at any Apple Store and perhaps someone will help you out for free. They should have some recovery discs on hand I hope! Good luck!

If that is the only one that shows (no Recovery HD) then your Recovery HD partition may be missing or damaged.

The -2002f error you got previously says your Wi-Fi network is not good enough to support downloading Internet Recovery Utilities. If you have an Ethernet port, you MAY be able to use that with your Mac (maybe closer to the Router) and connect using Ethernet.

in Internet Recovery, these low negative thousands error messages indicate that your provided Wi-Fi Network is inadequate in some fashion, and cannot be used in its current state.

Common problems include:

Hidden Network-name

required use of a proxy server to get Internet access

required use of a login page to get Internet access

Use of a login server or certificate to get Internet access

Use of PPPoE in the Mac to get Internet access (typically only applies to DSL)

Use of Fixed IP address rather than good old DHCP

Variance of the time by more than five minutes

Failure of Router to provide workable DNS server addresses, or providing 0.0.0.0 [may produce -2002f]

If you have an Ethernet port, you may in some cases be able to move your Mac close to the Router and connect to the Router using Ethernet.