Error when I try to open my Microsoft Defender

Hello Mandy

Thank you for sharing the screenshot. I understand that you can sign in to your Microsoft account online, but the Microsoft Defender app on your laptop shows "Unable to log into Microsoft Defender.”

Please try these basic steps first:

1. Update Microsoft Defender from the Microsoft Store.
2. Restart the laptop, then open Defender again.
3. Temporarily turn off any VPN/proxy and try signing in again.
4. If the issue continues, go to Settings > Apps > Installed apps > Microsoft Defender > Advanced options, then try Repair first. If that does not work, try Reset. After that, reopen Microsoft Defender and check whether you can sign in again.
5. If none of the above helps, uninstall Microsoft Defender and reinstall it from the Microsoft Store.

Please let me know how it goes so we could determine the best next steps if needed.

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