Get help using Back to My Mac

Update your Mac to the latest version of macOS.

On all of your computers:

• Make sure you're signed in to iCloud with your current Apple ID. If you changed your password but didn't update it in iCloud preferences on either computer, Back to My Mac won’t connect.
• Make sure Back to My Mac is turned on. Choose System Preferences from the Apple menu and click iCloud. In iCloud preferences, make sure Back to My Mac is selected and review any status messages. If Back to My Mac is selected, deselect it, then select it again.

On the Mac you're trying to connect to:

• In Energy Saver preferences, make sure your Mac isn't in sleep mode. Set it to either Wake on Demand or never go to sleep.
• If you're trying to share the screen, make sure that you set up screen sharing correctly.
• If you're trying to share files, make sure that you set up file sharing correctly.

On your AirPort Base Station or router:

• Update your firmware and make sure that your base station is set up to use Back to My Mac.
• Turn on NAT-PMP or UPnP. If you're not using an Apple router, see the documentation that came with your router for instructions for turning on NAT-PMP or UPnP.
• Find out if your network has a multiple-NAT configuration and update it if you need to.
• Make sure that the TCP or UDP ports used by Back to My Mac are open on your firewall. Contact your ISP if you need help confirming that these ports are open.

1. Go to Applications > Utilities > Keychain Access.
2. From the list of Keychains on the left, choose System.
3. Click the Kind column header to sort the Keychain list by kind.
4. Select all keys of the kind "Back to My Mac key.”
5. Delete the selected keys. You need to enter your administrator password.
6. Quit Keychain Access.
7. Choose System Preferences from the Apple menu. In iCloud preferences, deselect Back to My Mac.
8. Turn your Mac off and back on again. 
9. Choose System Preferences from the Apple menu. In iCloud preferences, select Back to My Mac.

If you still can't use Back to My Mac, contact iCloud Support. Here's the information you'll need:

• Troubleshooting steps you’ve already done.
• Network setup for each computer, including the makes and models of your routers and modems.
• Any status messages that you see in iCloud preferences for Back to My Mac. If you can, take a screenshot of each message.
• Results of the traceroute you performed on each computer when you checked for a multiple-NAT configuration.
• Computer name and local hostname of each computer.