Fix Windows Defender 404 Not Found Error on Windows 10
You click to open Windows Defender Security Center and see a 404 page, or the Settings app shows ...
Checklists for software errors, setup, and tool workflows.
1. Reproduce
2. Isolate
3. Apply
4. Verify
Latest checklists
View listHow to Fix Windows Defender Service Won't Start
When Windows Defender won't start, you'll likely see an error like "The service did not respond t...
How to Fix Microsoft Store Not Starting Automatically After Login
If you expect the Microsoft Store to launch when you log into Windows but it doesn't, you're not ...
How to Fix Task Scheduler Proxy Error
If you see a proxy error when running a scheduled task, it usually means the task cannot reach th...
Fix Windows Defender Stuck Loading Service Not Running
If you open Windows Security and see 'Windows Defender Service not running' or it hangs on a load...
Fix Outlook Proxy Error After Windows Update
After a Windows update, some users see a proxy error in Outlook—something like “Cannot connect to...
Topic paths
Quick titles
Fix Windows Search Error 0x80070005 Permission DeniedWindows Defender Registry Fix for Port Allocation ErrorRefresh Microsoft Store Token GuideHow to Fix SSH Host Key Verification Failed ErrorFix Windows Activation Login Loop Stuck on Sign-In ScreenStop Windows Update from Using Data on Metered Wi-FiWindows License for Boot Camp Mac: Complete GuideHow to Fix Windows Update Connection Refused by Proxy