Windows Defender Notifications Not Working — Even After Clean Installs, BIOS Reset & Full Repairs

Hi everyone, I’m facing a strange and persistent issue with Windows Defender notifications, and I’m hoping someone here may have encountered something similar.

During routine system maintenance, I noticed that Windows Defender has completely stopped showing notifications — no scan completion alerts, no threat‑found pop‑ups, nothing at all.

Troubleshooting I’ve Already Done

To rule out corruption, configuration issues, or hardware‑related causes, I’ve carried out extensive testing across multiple clean installations:

Reinstalled Windows using the Media Creation Tool → still no Defender notifications
Reinstalled Windows again using Rufus → same result
Reset BIOS / cleared CMOS
Installed an older Windows 11 build (offline, before updates) → still no notifications
Deleted all partitions on every reinstall (full clean install)
Verified all Windows Defender notification settings, including Enhanced Notifications
Checked Windows notification settings to ensure Windows Security is allowed
Ran SFC
Performed DISM /Online /Cleanup-Image /RestoreHealth
Confirmed no registry or Group Policy entries suppressing notifications
Reinstalled Windows Defender components
Scanned with third‑party tools and Microsoft MRT — no issues found
Ensured Windows Push Notification System Service is running

Despite all of this, Defender notifications never appear on any fresh installation.

Microsoft Support

I opened a support ticket with Microsoft.

One engineer performed an in‑place repair install
Another advised me to post the issue here for deeper investigation

Ticket reference: 710148747

Additional Technical Findings

1. Notifications are not being suppressed

No GPOs applied
No Intune configuration profiles
No registry entries modifying notification behaviour
Local notification settings fully enabled
Defender notifications fully enabled
It’s not a profile corruption
It’s not a user hive issue
It’s not a local DB issue
It’s OS‑level

2. Windows Notification Platform (WNP) appears to be the root cause

Across multiple clean installs:

ShellExperienceHost exists on disk.
Focus Assist toggle produces no toast (not sure it does)
other apps like mail, Logitech, steam can toast notification, i don't see defender toasting any scan notification.
WNP is partially working
Defender is partially registering
The scan‑completion channel is failing specifically

This behaviour is consistent and reproducible.