The most common reason is a missing or not registered .mp4 link in the Windows registry, with other reasons including a damaged Defaults cache or interference from software from other companies. In this article, we will discuss different ways to solve this error.
1. Reset the Movies & TV App
One common reason for this issue is a corrupted Movies & TV app (also known as Films & TV). This corruption can prevent Windows from saving another app as the default. If this applies to you, reset the Movies & TV app from Windows Settings. That’s it! Your chosen app should now be the default for MP4 files on your Windows 11 PC.
2. Install the Missing File Extensions
This issue can also be caused by missing codecs or broken file associations. You can use a trusted third-party package to install the missing codecs. Once they’re registered in Windows, you should be able to set your default MP4 app normally.
3. Downgrade to Windows 10
If none of the methods above work for you, you can roll back to Windows 10 until Microsoft releases an official fix. Downgrading is simple and shouldn’t take long. Note: The “Go back” option is available for a limited time after upgrading (usually up to 10 days), and only if the old Windows files are still present.
