Missing room

Hi all,

I recently moved Cortex from an aging Dell D820 to a Revo and all is working well however i've noticed that one of the rooms have dropped off the plan. It's still there in the structure but no longer on the graphical plan. I remember this has cropped up in the past but i've not been able to find any posts that explain how to get the room back. Can someone please point me in the right direction?

Thanks,
Nad