Major Windows updates often reset your custom default app registry choices back to Microsoft's recommended defaults.

• Open Settings by pressing Win + I.
• Navigate to Apps > Default apps.
• Search for your preferred web browser, PDF reader, or media player.
• Select the app and click Set default if available, or assign specific file types (like .pdf or .mp4) individually.

To see how to manually reassign file types back to your preferred applications in Windows, watch this guide: How To Fix An App Default Was Reset Notification Error in Windows 11

• Press Win + R, type cmd or Terminal, and run it as Administrator.
• Export your current configuration by running: Dism /Online /Export-DefaultAppAssociations:“C:\DefaultApps.xml”
• Press Win + R, type gpedit.msc, and hit Enter (Windows Pro/Enterprise only).
• Go to Computer Configuration > Administrative Templates > Windows Components > File Explorer.
• Enable Set a default associations configuration file and point it to C:\DefaultApps.xml.