You may have to reset the iOS device and see if you could re-download the app.
I've not tried Swift Playgrounds in my iPhone SE (64GB) iOS11.2.6, to read details
or try and find if I could replicate your loading issue here. There may have been a
bandwidth or ISP problem in the download - or perhaps files may have added too
much content to your device's storage memory as that could have bad effect in
program startup & loading. If capacity of storage is marginal, that could be reason
for stalling or failure to load. The app is kinda larger than most.
And my iPad Mini1.1 16GB (wi-fi) is too old to run Swift Playground. Did you set up
your Mac (or PC) to work with your iPad to utilize features of Swift? That's also an-
other of those details. {Sorry to not be of much help in this.} Perhaps a Community
Host could relocate this topic thread to another ASC... such as the one for Swift?
In any event...
Good luck & happy trails! 🙂