Can't open display

This error message usually indicates that the X11 server is not running or that the DISPLAY environment variable is not set correctly. If you are trying to run a graphical application from a remote machine, you may need to use SSH with X11 forwarding enabled in order to display the graphical output on your local machine.

To enable X11 forwarding with SSH, you can use the -X or -Y option when connecting to the remote machine. For example:

ssh -X user@remotehost

Alternatively, you can try setting the DISPLAY environment variable manually to the appropriate value for your system. The exact syntax will depend on your operating system and the configuration of your X11 server. For example, on a Linux system running X11, you might set the DISPLAY variable like this:

export DISPLAY=:0.0

If you continue to experience issues, you may need to consult the documentation for your specific operating system and X11 server for further troubleshooting steps.