Making embedded MS Form wider on screen

Hello,

I've embedded a MS Form into a training made with Rise 360 using the following iFrame code (without the redaction, of course):

<iframe width="640px" height="480px" src="https://forms.office.com/Pages/ResponsePage.aspx?id=[redacted]&embed=true" frameborder="0" marginwidth="0" marginheight="0" style="border: none; max-width:100%; max-height:100vh" allowfullscreen webkitallowfullscreen mozallowfullscreen msallowfullscreen> </iframe>

I am new to iFrame and Rise, but I've played with numbers in the width= of the code to try to make the embedded form wider on screen. This doesn't seem to have the effect I want. What should I be doing to make the form wider? Or is this something that cannot be changed?

Thanks for your help!