Search not returning results

First off, there could be multiple potential culprits behind the search issue you're facing. A good starting point would be to inspect the search schema. Ensure the columns you're searching against, like folder names, are included and marked as crawled properties. Check this under the Search Schema section in Search Administration. Another avenue to explore is verifying the search crawl status. Head over to Search Administration and confirm the crawl is completing successfully for your site collection and that content sources are correctly configured. An incomplete or failed crawl could lead to outdated or missing search results.

While you're there, it's worth confirming the search settings scope is appropriately defined. If set too narrowly, it may exclude relevant results from other locations. Adjust as needed. Additionally, try clearing the search cached results, as stale cached data might cause inconsistent search behavior. Look for the "Search Cache Accounts" section in Search Administration and clear the cache for your web app or tenant.

Furthermore, review the crawl log files for any errors preventing content from being crawled and indexed properly. These logs reside in the "Crawl Log" section of Search Administration. As a last-ditch effort, you could attempt restarting the SharePoint Search Services, assuming you have access. A service restart sometimes resolves transient search issues.