The Find an Item search box isn't producing results when I enter criteria for it to search.
Is there a way to enter ID numbers to search by ID?
First check if the list has been crawled properly. Please go to the CA check the search service applications. We can search the crawl log ensure the list items have been crawled. After that, here is something for you to check:
- Check if URL of site to which the List belongs is being added to the Content Source in Search Service Application.
- Re-index the list from advanced settings of the List
- Run a full crawl in Central Administration and test again.
If there are multiple lists on same site affected you might want to index whole site: Site Settings -> Search -> Search and Offline Availability
More information about general solution for list search:https://www.c-sharpcorner.com/article/sharepoint-search-your-search-returned-no-results/