Search primary field custom entity

We have a custom entity (product code) with a primary field as a single line text field type. We have selected Searchable in the field properties for this primary field. We cannot get the field to provide any results in the search areas that it should such as - search on entity view, search from lookup field. The field and entity have been published with data long enough (over 60 days) that any search crawl should have been done.