OK, I think I figured it out. Basically I needed to put the acf_form_head() function call before my DOCTYPE was even declared, so I did that on my header.php file and not in the custom page template I created.
I figured this out after trying to use the form to create a new post type and getting a whole bunch of PHP warning: Cannot modify header information.
Just tried the same method with the standard front-end form that doesn’t create a new post type and it’s also working when acf_form_head() is called before DOCTYPE (or anything else). Seems obvious to me now but wasn’t clear from the tutorial section that it needed to be outside of the custom page template.
