Happy to.
Stop Sale means that the tour operator has suspended sales to that hotel. It could be for just a few dates or the whole of the season and for many reasons, including re-negotiating room rates or allocation, an investigation into complaints or if the hotel has notified that an important service has been withdrawn and it needs to be taken off sale until the new brochure is out. The list could be any of those, or even some other reason, the sales team won't be told.

Hope this helps.

Thanks Agent Q - so even though it is listed in the Wintersun brochure for the dates, it won't necessarily be available? Would there be even the slightest chance that it would be listed in the summer brochure for those dates? If not we might as well start looking elsewhere.