In order to install the XPS Viewer app on Windows 10, do the following:
- Open Settings.
- Click on Apps.
- Click on Apps & features.
- Under "Apps & features," click the Manage optional features link.
- Click the Add a feature button.
- Select XPS Viewer from the list.
- Click the Install button.
After completing the steps, the XPS Viewer will install on your computer, and you'll once again be able to open files stored on your computer using this file format.