The tables displayed in the Global Search Results are defined in Search Groups. So verify if a search group exists for the specific table and if that is the case, then review the condition in the search group in order to display the desired records.
2. Review if there is an existing group for the specific table or tables. Only a few search groups exist in an Out of the box instance.
3. If the search group exists, then review if the condition is correct to display the desired records.