Issue with UMUI Startup

I am trying to open the UMUI window. However, every time I type the command umui & in the terminal, I receive the following error message:

I would be grateful if you could let me know how to solve this issue.

Many thanks.

Hi Irene,

Please make sure you are use ssh -Y on every login to set your DISPLAY.

Regards,
Ros.

Thank you, it worked.
Irene