The thing about Windows Update services (WU or WUS) is that so many things can go wrong. Microsoft provides a Windows Update Troubleshooter that you may want to try before messing around with items manually, but we've found it rarely solves issues when Windows Update is acting up.
First off, look in the Application event log for events with Event ID 1001 and the "Information" level. The Event Name for WU issues is "WindowsUpdateFailure3" and typically paired with a fault bucket of type 5. In the problem signature, look for the code in the P2 line (such as 80246008 or 800706d9). Those are the codes you will want to include in your Web searches to see if you can find the exact cause of your issue.
If that fails to provide you a solution or you just want to reset Windows Update without having to troubleshoot too much, we've found that the following general steps fix ~90% of Windows Update errors. This should work in Windows 7, 8, 8.1, 10 and most flavors of Windows Server.
Continue on for the steps and some great tips...
- Verify that the Windows Firewall service is running and set to Automatic.
- Yes this is a required service. It doesn't have to be enabled, but the service needs to be running. I don't know why this isn't including in most sites that help you troubleshoot but it's easy to check for and if it's not running you will likely have WUS issues.
- Stop both the Windows Update & Background Intelligent Transfer Service (BITS) services.
- After stopping the Windows Update service, refresh your view of the services (F5 if using the Services MMC) and make sure that it didn't restart itself. If it did, stop it a second time.
- Delete the C:\Windows\SoftwareDistribution folder (or rename to C:\Windows\SoftwareDistribution.old), essentially clearing the Windows Update download cache so that it can start over.
- Delete all files out of C:\ProgramData\Microsoft\Network\Downloader.
- Reboot your computer.
- If you are in an environment where you cannot reboot the computer, such as on a production Windows Server 2016 machine, then you can just start the BITS service first and then start the Windows Update service after that and it should still work. We just recommend restarting to clear out any other possible issues.