Note: a portable Mac will not wake unless connected to an AC power source.

Check the Mac's Energy Saver settings

• On the Mac you wish to connect to, open System Preferences.
• Click Energy Saver.
• Click Power Adapter.

• Ensure that Wake for Wi-Fi network access and/or Wake for network access is enabled.
• If this was already enabled, disable Put hard disks to sleep when possible.
• Click the Apple menu in the system menu bar.
• Click Sleep.

Turn your attention to Screens and attempt to connect to the Mac. If the Mac doesn’t wake, and the above mentioned hard disk setting was enabled for this connection attempt, go back and disable this feature, then try connecting again.

If the Mac doesn't wake and the connection fails:

• Open System Preferences.
• Click Energy Saver.

• Enable Prevent computer from sleeping automatically when the display is off.

Try connecting again. If the Mac still doesn't wake, consider the following...

Is the Mac's system volume encrypted with FileVault?

Your Mac's FileVault feature could be interfering, especially if you find that a user must physically log into the Mac before Screens can connect:

“To ensure security when you turn on FileVault, other security features are also turned on. For example, when you turn on FileVault, you need a password to log in when your Mac is in sleep, or after leaving the screen saver.”

There are a couple of work-arounds available to you:

• Disable FileVault. See Apple's support document for instructions: https://support.apple.com/kb/PH25416
• Restart the remote Mac with the following Terminal command to bypass the start-up authentication required by FileVault: sudo fdesetup authrestart

References

• macOS Sierra: About FileVault encryption
• macOS Sierra: Encrypt the contents of your Mac with FileVault
• macOS Sierra: Turn off FileVault encryption
• Restart a remote Mac that is running Filevault 2