This typically indicates that a network routing problem is preventing Screens from contacting the remote computer.
The computer is in sleep mode, is turned off or not plugged into a power outlet
See this article to learn more about how to make your Mac wake up for incoming connections.
Firewall or Screen Sharing Service Issue
Some users reported that the built-in macOS Firewall would prevent incoming connections and turning the Firewall off would restore connectivity. The workaround for this issue is to disable Screen Sharing (or Remote Management), re-enable the service and restart your Mac. This should reset the Firewall rule and allow you to connect.
If you are connecting to a remote computer across the Internet, we strongly recommend that Screens Connect is installed on the remote machine and that you're signed into Screens and Screens Connect with your Screens ID.
Virtual Private Networks (VPN)
Are you trying to connect through a VPN? If so, note that many VPNs prevent Screens from establishing a direct, two-way connection with other computers. We recommend a secure/encrypted Screens connection instead of routing your connection through a VPN.
Dynamic routing prevents Screens from establishing direct, two-way connections. A possible solution is to request a static IP address from your Internet service provider.
- Consider the public IP address for a moment. If the address is something like 100.64.x.x, your address is part of a dynamic pool of addresses managed by dynamic routing.
- Is your router’s public IP address really what the Internet thinks it is? To find out:
- Using the computer you intend to connect to, visit whatsmyip.org.
- Compare the IP address listed on that page with the public IP address you collected earlier.
- If the IP addresses differ, Screens is unable to establish a direct, two-way connection with the computer you intend to connect to.
Local-Network IP Addresses
If you’re using a static local IP address for the computer you’re connecting to, does it follow the same pattern as the gateway’s internal (LAN) IP address? If this address is something like 192.168.0.1, the static address assigned to the computer you intend to connect to should be something like 192.168.0.xxx.
Check the local hostname listed in Screens for the remote computer. Compare this with what’s listed in Terminal.app when you enter the following command:
If they are different, please see this Apple support document:
Make sure that the gateway’s public port is open for connections from the Internet:
- Visit https://canyouseeme.org.
- Enter your public IP address.
- Enter the public port number.
- Click Check Port.
If the port isn’t open:
- Refer to your Internet gateways’/router’s firewall and other security settings and make sure there are no configuration issues that might interfere with Screens.
- If you’re using a custom port forwarding rule for Screens, make sure that the gateway’s public port is forwarded to the remote computer’s local-network IP address and its port 5900 for Remote Management or port 22 for Remote Login.
- Check any network security or anti-malware applications installed on the remote computer to make sure nothing is interfering with Screens, such as the following (click each for help):
If nothing has helped so far, please reproduce the issue and send a diagnostics report. We’ll be happy to review the information and offer any help we can.