sharepoint enterprise – KQL for specific columns that do not work

I have a SharePoint 2016 local farm that contains a large list of items with several text fields that should be searchable.

Title Name Date of construction approval Category

Each of these fields must be searchable. Performing a standard search in the list returns the correct results. For example, the search for "333" will return all drawings that contain 333 in any field. However, when trying to search for a specific field using KQL, I do not get any results. I am trying to find the value "333" in the Construction field. I tried to search using the syntax Building: 333, Building: 333 * and Building:333. None of these queries returned any results. I can go to the list view and filter by the construction column and it returns the correct results. I have tried searches in other columns with the same results. I also tried to search by filtering empty buildings using the syntax Building <> "". Instead of returning no results, this returned ALL the elements of the list, including those in which the Construction column was empty.

This is the first time that I try to use KQL, so it is very possible that I do not have something configured correctly or that a required function is not activated. However, at this point, I do not even know what to look for. Can anyone tell me why this may be happening?

I have also verified that my search index is running correctly and all drawings appear to be indexed, as they are displayed in searches that do not use KQL.