The issue relied in CSS. I’m not sure if the conflict was because of my theme or something in your code, but in case anyone else has the issue that’s what I used to fix it.
Previous DISPLAY setting made my form to not display if the “this field is required” error message was supposed to appear.
display:block fixed the issue.
body .pieregWrapper *, body .pieregWrapper li, body .pieregWrapper ul, body .pieregWrapper img, body .pieregWrapper div, body .pieregWrapper a, body .pieregWrapper p, body .pieregWrapper input, body .pieregWrapper label, body .pieregWrapper span, body .pieregWrapper h2, body .pieregWrapper h1, body .piereg_container *, body .piereg_container li, body .piereg_container ul, body .piereg_container img, body .piereg_container div, body .piereg_container a, body .piereg_container p, body .piereg_container input, body .piereg_container label, body .piereg_container span, body .piereg_container h2, body .piereg_container h1, body .linkStyle1 {
display: block;
}