Thanks for reporting this - I can reproduce the issue and so I’ve created a card for it and it will be looked into by our development team.
In the meantime, also try the ‘import from GitHub’ option found under Advanced Options from the top-left Project Info menu in the editor. Note that it’s Chilace/Discord.RSS not the full URL when asked which project to import. I’ve been able to import this repo that way without issue.
The problem was the ‘.’ in the project name. We try to base the Glitch project name on the GH repo name, and we don’t allow ‘.’ in project names. This is fixed - it now gets replaced with a ‘-’.