You are unable to open a .pps (PowerPoint 97-2003 Show) file.
PowerPoint isn't installed on your computer.
Use a desktop version of PowerPoint (on Windows or macOS) to open the file.
You may also be able to use PowerPoint for the web or a mobile version of PowerPoint to view presentations. See View a presentation without PowerPoint for more information.
You can open a PowerPoint Show (.ppsx or .pps) file in PowerPoint for the web or a mobile PowerPoint app, but you can't edit the file. However, once you've opened the file, you can save a copy of it as a .pptx file and then edit that file.