Updates made to an embedded Form are not immediately reflected on the web after the Form is approved.
To improve page load times, Marketo Forms are served from a cache. It may take up to 4 minutes for newly approved changes to forms to display on the web. This only applies to embedded forms on non-Marketo pages; forms on Marketo Landing Pages will continue to update immediately after approval.
To preview changes immediately, you can use the Preview functionality. https://docs.marketo.com/display/public/DOCS/Preview+a+Form