Embedded form on WordPress site refuses to direct to THANK YOU page

I have an embedded Marketo form on a wordpress site. No matter what we do, I can't get the form to direct the user to the appropriate thank you page. Even when this page is a marketo LP. The form simply submits and hangs. Marketo support won't help me because it isn't a Marketo LP. My dev can't figure it out. There's no javascript errors in the console. Any advice here folks? There's a marketo embedded subscribe form in the footer - could that be causing a conflict?