On my side, I get the same error if the url I want to summarize ends with a /
.
I tested with this URL: https://www.wired.com/story/linda-yaccarino-says-x-needs-more-moderators/
which results in:
http://!sum%20https://www.wired.com/story/linda-yaccarino-says-x-needs-more-moderators/
If I remove the /
from the end it seems to redirect correctly to the summarizer.