If the Cross Sell Gallery is showing "SOLD OUT" under the displayed listings, this is because those items have been displaying for more than 30 days. After 30 days, the item is relisted automatically by eBay, and due to technical limitations from eBay, the duration doesn't update in the gallery and will therefore displays as "SOLD OUT".

In the template editor, a rectangle element can be added and placed over the sold out text to hide it from view:

To easily reapply the template after making the change, click the arrow next to the "Save" button at the top right of the template editor, and select "Save & Apply All". This will reapply the template to all listings which are already using that specific template.