Iframe - submit via jquery

Hello,

I got two websites A and B. B includes A using an iframe.

The page on site A contains a form and some javascript (using jquery).
The form on site A gets submitted using jquery - i.e. $("#frmXXX").submit();

This works well in edge (chromium) when I open the site directly. When I try to submit the form using Site B (A included using an iframe) nothing happens. I get no error, nothing.

Am I missing something? Is this a bug?

My version:  82.0.439.1 

Thanks for your help!