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"Paint 3D
Paint 3D was deprecated in August 2024 and was removed from the Microsoft Store on November 4, 2024. Existing installations of Paint 3D will continue to work, but the app will no longer be available for download from the Microsoft Store. If you remove the app, you can reinstall it from the Microsoft Store until November 4, 2024. After that date, Paint 3D will no longer be available for download. Paint 3D was preinstalled on some Windows 10 devices, but wasn't preinstalled on Windows 11 devices. Some alternatives to Paint 3D include:
View and edit 2D images: Paint or Photos
View 3D content: 3D Viewer."
Source link: https://learn.microsoft.com/en-us/windows/whats-new/deprecated-features-resources
Alternatively, you can go to the Microsoft Store and install other 3D painting apps like Blender.