Ping is not working
First, make sure your device is authorized on the network and you're using the ZeroTier assigned Managed IP address. Aside from that, some OSes block pings in their local firewall by default.
ZeroTier versions 1.10.3 and greater automatically enable ping on ZeroTier adapters.
The firewall is not enabled by default on macOS, and thus pings will not be blocked by default. If your firewall is enabled on macOS, go into System Preferences -> Security & Privacy. Under Firewall Options, ensure "Enable stealth mode" is disabled. Stealth mode blocks pings.
There are far too many Linux distributions out there to list instructions for all of them here. Please refer to your distribution's documentation for how to unblock ICMP packets.
Click here to create your network and start adding devices.
Error: Cannot connect to ZeroTier service (or Node ID "Unknown" in the GUI apps)
This error means that the ZeroTier background service on your computer is either not running, or your local firewall is preventing the UI or CLI from talking to it.
Open Task Manager and go to the "Services" tab. Scroll down until you see "ZeroTierOneService". The status column should say "Running". If it does not, right click on the line and click "Start"
Open Terminal.app and execute the following commands
sudo launchctl unload /Library/LaunchDaemons/com.zerotier.one.plist
sudo launchctl load /Library/LaunchDaemons/com.zerotier.one.plist
If your Linux distribution uses systemd, execute:
sudo service zerotier-one start
If not, execute:
Still doesn't work?
Your system firewall is likely blocking communication with the ZeroTier service. Look up instructions for how to unblock an application from the firewall for your OS. ZeroTier will need to be accessible via TCP port 9993 for the UI and CLI to interact with it.