Hi, Karen. Sorry you’re experiencing this.
I was able to reproduce this issue with that URL. It eventually timed out for me with this message:
The preview is taking longer than expected. Please try again in a moment.
When I re-tried it, I then got this message:
There was an error fetching the results from your import: The import is in progress.
As a temporary workaround, could you please test to see if downloading the basic.ics file to your computer and then uploading it at wp-admin > Events > Import > Import Origin = ICS File then allows you to import it?