Could you expand on your workflow a bit? I don't use Publish Online myself, but I don't believe that you'd be able to insert PowerBI content in this way. Wouldn't you need to generate a static report, and save it in a format that can be placed in InDesign?
I doubt Adobe is "approving" all websites inserted as an iframe. I would imagine that the path as to have a certain format. What is the format/structure of the address you are trying to put in the iframe? (you can x out critical info to keep it private.)
David Creamer Adobe Certified Instructor, Adobe Certified Professional, and Adobe Certified Expert (since 1995)