Thank you for reaching out to the Zoom Developer Forum. Interestingly, I’m able to reproduce the issue with the URLs that you provided by when substituting my own Registration Required Meeting UUID I don’t see the same issue. I’ve reached out to our engineering team for clarification.
Thank you for your patience. It looks like there are a couple of factors playing into this. First, the List Meeting Registrants API will only accept a Meeting ID as it expects to operate on a meeting occurrence in the future rather than a meeting instance in the past.
Further, because this UUID contains a slash, it caused the API to return a 200 OK status instead of an “Invalid Meeting ID” error.
From here, you should be able to use the Meeting ID along with the occurrence ID to refer to the meeting instances scheduled in the future that have been registered for.
I hope that helps! Let me know if you have any questions.