I'm wondering if it's similar to the issue I've been seeing on our embedded reports. I'm not seeing it in the few publish to web I have, but am getting an error with secure embed or SharePoint embed. Considering they all use some sort of embed code/link, seems like something is up.
I entered a ticket with MS, the technician promptly responded with the following action: "I run a backend fix on your tenant and you confirm that the URL is now working fine." This resolved our issue.