If you ever see a warning message on Gnomen telling you that a property is on hold/occupied you will need to edit the internal status of a property. Follow the steps below:
Go onto the property that is on hold/occupied > press on actions > then click on edit property
The head over to step 3: more info > then change the internal status of the property from hold/occupied to available
This should allow you to create sales and new tenancies for this property.