this question is related to my previous question which not been answered. When I go to Search Schema I can find the corresponding managed property for the Managed Metadata Site Column, and I it is bound to a Crawled property (owstaxIdMySiteColumn is the Managed Property). It is marked as selectable, queryable, searchable and refiner everything. Does it mean that it is indexed? if it is indexed why I cannot filter my search based on it? I mean if I search based on the contentTypeId it returns all Items in the list, but when I filter based on the managed property it returns nothing. and I send "selectproperties=owstaxIdMySiteColumn" but it does not returns the column at all, even with selectproperties=MySiteColumn the column not be returned.
Did you added site column as a Taxonomy field yet if not then follow this blogpost,
Can you also confirm if you went through all of relevant steps in this post,