Fail to fire an event to Google Tag Manager

Hi,
I embedded a survey as an iframe on LP.
I'm trying to fire few events (questions steps + survey submissions) to GTM.
I've embeded the GTM code at the "header" of the survey using the look&feel section, and added to the 1st question this code "dataLayer.push({'event': 'first_step'});", the second one this code dataLayer.push({'event': 'second_step'}); and so on...
Unfortunately, I'm not able to fire the survey submission to GTM. I've embedded the following code at the end of survey message:
Google tam manager code + "dataLayer.push({'event': 'final_step'});"
Could anyone help solve this issue?

Thank you,

Roy