Written for Synergy 1 (v1.21.4), checked 3 October 2026.
Find the message you see below; each one starts with what to do. For anything not listed, send us your log: Saving the Synergy 1 log to file
Connecting
Address missing
Type the server's name or IP address in Connect to: on the client, then click Connect. The server shows its address in its own Synergy 1 window, next to Suggested IP:.
A Client with your name is already connected to the server.
Give each computer its own name: stop Synergy 1, click Edit Computer Name, type a name no other computer uses and press Enter. Also make sure Synergy 1 is open only once on this computer. The window title is Synergy Connection Error.
A new client called '...' wants to connect
Click Add client to place the new computer in your layout, or Ignore to refuse it until Synergy 1 restarts. If encryption is set to require client certificates, you'll see A new client called '...' has been accepted instead; add it to your layout with Configure Server. Arranging the layout: Arrange your computers in Synergy 1
Connecting to a new server, or New client connecting
Compare the fingerprints and click Yes only if they match. How: Encryption and fingerprints in Synergy 1
Missing Keyboard Layouts
Install the keyboard layouts listed in the message on this computer, so it can type the other computer's characters. If you don't need them, tick Don't show this again.
Starting
The Core executable could not be started.
Reinstall Synergy 1 so its files and permissions are restored: How to reinstall or uninstall Synergy 1
On a server, the message can also name the server configuration file. Check that your account can read it (and write it, unless you use your own config file), or choose a file you can read on the Config file tab of Configure Server.
Background service offline (Windows)
Click Retry. If it appears again, restart the Synergy service in the Windows Services app and click Retry once more. If you stopped the service on purpose, click Disable to run Synergy 1 without it (this turns off Use background service (daemon) in Preferences; without it, Synergy 1 can't control the login screen or UAC prompts). Ignore closes the message and changes nothing.
Synergy is already running
Synergy 1 is already open. Look for its icon in the notification area (the menu bar on macOS) and open it from there.
Please drag Synergy to the Applications folder, and open it from there.
On macOS, Synergy 1 won't run from the downloaded disk image. Drag it to Applications and open it from there: Installing Synergy 1 on macOS
macOS asks to allow Accessibility
Synergy 1 closes until you allow it under Accessibility in System Settings. The steps: Troubleshooting macOS Device Control and Data Access (previously Security & Privacy in Accessibility)
Settings
Invalid Screen Name
Use only letters, numbers, _ and -, between 1 and 255 characters, and a name no other computer in your layout already has (Screen name already exists).
Read-only settings
Your account can only read the settings file named in the message, so changes can't be saved. Ask your administrator to change the settings, or open Synergy 1 as an administrator if you are one. On shared computers this is usually deliberate: Configure Synergy for multi-user support
Filename invalid: Please select a valid configuration file.
In Server Configuration, the Config file tab points to a file that doesn't exist. Click OK and pick the right file, or untick Use a server config file.
License
Activation failed
Follow the advice in the message: free an activation on your account page and click Start again, or click Change serial key if the key is wrong. If you contact us, include the License reference shown in the message. How activation works: How license activation works in Synergy 1 and Synergy 3
Serial key problem
Invalid serial key. means the key isn't complete or correct: copy it again from your account page and paste it in. Sorry, that serial key has expired. means it's time to renew. Entering a key: Enter or change your serial key in Synergy 1
Unexpected errors
Sorry, a critical error has occurred.
Copy the text in the box and send it to our support team, with your log if you can. Click OK to carry on, or Ignore to stop that same error appearing again until Synergy 1 restarts. If the message says Sorry, a fatal error has occurred and the application must now exit., Synergy 1 closes after you click Abort; open it again.