The file you selected,
contents.xcplayground, is an XML file. Swift playgrounds require Swift code to run. If you select the file
Contents.swift, are you able to run the playground?
The contents of what you downloaded look different than any playground I have seen. Every playground I have created and opened is a file package with the extension
.playground that has the files
contents.xcplaygrounds and the Sources folder inside the package. What you downloaded is the contents of the playground in a folder instead of a file package with the
.playground extension. What is the URL of the repository where you downloaded the playground?