Try these checks in order:
- Run the Search and Indexing troubleshooter.
- In Windows 10, go to Start > Settings > Update & Security > Troubleshoot.
- Find Search and Indexing and select Run the troubleshooter.
- Verify the Windows Search service is running.
- Open Start, type services.msc, and press Enter.
- Find Windows Search.
- Set Startup type to Automatic (Delayed Start).
- If Service status is not Running, select Start.
- Check whether indexing is still in progress.
- If indexing is still running, search results can be incomplete.
- Leave the PC on and connected to power for a few hours so indexing can finish.
- If the device is busy, indexing can slow down or wait until the PC is idle.
- Make sure the correct folders are included in indexing.
- Open Searching Windows and select Advanced Search Indexer Settings.
- In Indexing Options, select Modify and confirm the folder that should contain the missing item is included.
- If search still misses files, rebuild the index.
- Open Control Panel > System and Maintenance > Indexing Options.
- Select Advanced.
- Select Rebuild, confirm, and wait for the rebuild to complete.
- Restart the PC after the rebuild.
- If the missing item is hidden, enable hidden files in search.
- Open Organize > Folder and Search Options > View.
- Under Hidden files and folders, select Show hidden files and folders.
- If the file is outside the index, search file contents.
- In Folder and Search Options > Search, select Always search filenames and contents (might be slow).
- This can help find files whose content matches the search term even when the file is not indexed.
If the issue is specifically that search is very slow or the Windows Search service fails to start, third-party registry cleaner or PC optimization tools can cause this by removing or corrupting Windows Search registry values.