Problem With Windows Defender Updates.

Hello, We have a problem with Windows Defender updates which started on Tuesday. Our PC is Windows 11 23H2 22631.2861 and is up to date. We use Norton 360 and so Windows Defender is turned off which is what it shows in Windows Security, although Defender definitions are downloaded which isn't the case with our other machine. I can't access Defender to manually update from Windows Security without uninstalling Norton. Recently, when I have been manually checking for Windows Updates a Defender Definition is downloaded to 88% and doesn't start installing. The only way to get it installed is by rebooting. Strange thing is I can manually install them during the day with no problem - just seems to be first thing. I usually pause Windows Updates and resume updates next day, not sure if that means anything. I did a repair install of Windows 11 but no change. I would be grateful for any suggestions. Thanks Mitch.

1) Uninstall Norton software with the applicable uninstall tool:



2) See if these troubleshooters make any changes:

https://aka.ms/EasyFix_WinSecurity

https://support.microsoft.com/en-us/...2-607b0cbd7fc4

Hi. Thanks for replying. I uninstalled Norton 360 using the removal tool and rebooted. I turned everything on in Windows Security and ran both troubleshooters. Both showed the same message - "We cannot detect the status of your firewall". Next "Problem Found - Windows Firewall Is Not The Default Firewall. Not fixed" I checked Windows Security. Firewall and Network Protection - Microsoft Defender Firewall - On.
Under security providers - Anti Virus, Microsoft Defender Is Turned On. Firewall, Windows Firewall Is On. I assume if Windows Security says the Windows Firewall is on then that's OK. The troubleshooter did not make any changes. Thanks for your help Mitch.

Hi @mackie . I tried a repair install first with Norton in place bur the Defender definitions still didn't install. I then uninstalled Norton and Reflect (to remove the licence) and did a clean install. I didn't reinstall Norton (on this PC) although Norton is on 2 others. If you use Norton, you have no access to Defender settings and manual updates unless you uninstall Norton. This desktop PC is different from the other 2. If I run WU check it will download definition updates which appear in Update History- in the other 2, no definitions are downloaded and don't appear in Reliability Monitor which shows installations. No one, seems to know why this is as all 3 PCs were setup the same way. Regards.

The only thing I can suggest is that if you have a backup or restore go back to prior Tuesday (per your opening post).