I created the page but am not sure how to add/embed the Nintex form in the web part?
Sorry its actually an app part and not a web part.

I have been testing and nothing is working. I keep getting a File not Found error.
I came across the following article. It looks as if I can't embed the responsive form:
https://community.nintex.com/t5/Nintex-for-Office-365/List-Forms-Online-showing-File-Not-Found/m-p/107504#M12501
Dont think that is correct.

The one part I am struggling with is the site URL. Here are the variations I have tried and the result in bold:
https://acme.sharepoint.com/sites/acme-IT FILE NOT FOUND
https://acme.sharepoint.com/sites/acme-IT/lists Web Part configuration incomplete: • Site Url is not valid.
https://acme.sharepoint.com/sites/acme-IT/lists/testlist/Alltems.aspx Web Part configuration incomplete: • Site Url is not valid.
The first one should work. Maybe the hyphen is causing an issue. Try a site that does not have one.
Is it responsive or New Responsive? I havent tested New Responsive.
The form was built using New Responsive.
The Current Limitations document advises that the New Responsive forms are not compatible with the forms web part.
https://community.nintex.com/t5/Responsive-Forms/New-Resposonsive-Office365-Current-limitations/m-p/89047