The Room Status can be changed from Vacant Tenantable to Vacant Untenantable when the Room is vacated, and you are unable to Tenant someone in that Room as it is being cleaned, needs to be inspected, maintenance needs to be carried out on the Room, etc.

To change the Room Status in a Property, you must go in to the Property Screen. 

From the Home Screen, click Properties, then click Manage Properties and double click on the row of the Property you want to change the Room Status for.  Once in the Property Record, to make a Room Vacant Untenantable, double click on the Room you want to change the status for. The Room details pop up will open:

Enter the date the Room will be Vacant Untenantable from in the Will be Unavailable From field:

When you have entered a date in the Unavailable From field, click 

You will see a pop-up box advising you that the Room status has been changed to Vacant Untenantable: