Using the on-line version of Twine 2.0.8 I tested the same two URLs you used on Windows 10 in the most recent releases of both Chrome and FireFox, and except for the standard perpetually spinning Loading message (which I cancelled after 10 seconds) both of the story formats successfully installed.
They are currently testing the next release of Twine 2, so I suggest that you visit the project website and create a new issue.
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They are currently testing the next release of Twine 2, so I suggest that you visit the project website and create a new issue.