For anyone interested the solution appears to be as follows;

Do not follow the instructions provided here which advise to create a custom event. These are out of date.

Make sure that you use the prebuilt “From Submission” trigger within GTM. The Form Submit event will not fire unless you have used this.

Hey @Sam_McEwin! Sorry about the delay getting an answer on this post. We are working on updating our documentation but since we have updated the code on our script manager to add GTM and GA, you should be able to track events on GTM by just using the Form Submission trigger on GTM. No need to use the gtm.formSubmit anymore.

Thanks for pointing that out. 🙂

Thanks. It’s the same thing though. The form submission trigger “listens” for the gtm.formsubmit event. So same same.

Sir… I have seen the difference in browsers. In google chrome, it is showing that tag is fired for submission but not showing data layer variable values. But if i see same in firefox… it shows all values for data layer variable but not showing form submission tag is fired. And if i submit form from firefox, then form tag does not fired and doesn’t show in google analytics… but in case of google chrome it fires and shows in google analytics. Please help me to solve this. Thank you!