We currently have a site in SP that the client wants to have more exact search verticals on, based on what folder the document is in.
I've configured a replica of the area in a test site (/mds/) and added a workflow that scans the absolute URL and uses a dictionary to find if a given value (folder name) is there. If it finds it (i.e. if index of string search > -1) it places this value into a field called 'Region Key'. So far so good, all this works.
The site has a search center sub-site, with the Site Settings of the site set to use this (Search Center URL set to /search/pages under Site Settings > Search Settings, with 'Use same results page as my parent' cleared).
Search results work OK from the site after doing this.
The problem occurs when I add a new results page to /search/pages and edit the Search Results WP - I can see the Region Key field as an available choice (after creating it as a managed property mapped to the correct crawled property).
Whatever value I specify for the field in the query returns zero results, even when this has been indexed and shows when it's used as a term in a normal site search.
Any suggestions? I've set up new verticals before in the same farm the same way, but based on the Content Type rather than a string value. Am I missing something obvious?