I have been able to display iframes of various sites without difficulty
For some reason the iframe below shows up blank.
<iframe src="https://seektable.reference.solutions/public/report/c9a02610466c4c0f9fce74792107d8eel" width="1000" height="1000"> </iframe>
The page itself resolves fine in a browser. I have added https://seektable.reference.solutions to my my approved iframe sources under settings.
Why might this particular domain not work when others do?
(It is my domain and the underlying web app and its report links are intended for iframe use; there is no x-site prohibition.)