I need to embed a couple of Microsoft Forms into a WordPress site.

I've tried the two obvious iframe plugins on the WordPress store (advanced and simple) and also a custom HTML block.

In each of these I am able to successfully embed a youtube video but all three exhibit the same behaiour when trying to embed a Microsoftform, which is that is creates and appropriately sized block but there is nothing visible within the iframe itself.

See this picture

The top blank section is supposed to have the MS Form, the bottom is a sample youtube video.

In both I've added a simple iframe block into a customHTML block.

The youtube embed is :

<iframe width="560" height="315" src="" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

A test MS Forms embed is :

<iframe width="640" height="480" src=".aspx?id=HjS5Mwk5TES-wbZx9qRH_uhj7Jye-YhDukl12cHhNLZUMFJTWEFNODRPUFA0NkJNUFBZM0taWUxJUS4u&embed=true" frameborder="0" allowfullscreen> </iframe>

I guess at this point it'll be an issue with the MS site but I'm not sure how best to test this or move it along.

Wordpress and all plugins are up to date.