Content Search Web Part Sort Not Working

I have created a content search web part but I cannot get the sort to work.

I want it to sort by the Site Name in alpha order, so I went into search schema and set the ows_SiteName to the mapped crawled properties for RefinableString02 . I did this several days ago (I should say that I am on SharePoint Online and cannot prompt a crawl). 

However, it seems to be working in my search site - when I select the refiner of RefinableString02, I see all the site names in alpha order. 

But it is not working in my content search web part. In the sorting panel, I select RefinableString02 and the order is not alpha. Is there an additional step that I have to do for it to sort alphabetically in my content search web part?

BNM OBG