For those using Divi 3.4 and newer, you will need to add some CSS to correct the form. Again, this is ONLY for those using Divi version 3.4 AND newer. If you are using an older version, you do not need to add this CSS.

To correct the form after the version 3.4 update, add the following to your child theme stylesheet or Divi > Theme Options > General > Custom CSS:

.ds-advent-4 .et_pb_newsletter_form, .ds-advent-4 .et_pb_newsletter_description {
width: 100% !important;

.et_pb_newsletter_description, .et_pb_newsletter_form {
float: none;
display: table;
margin: auto;
width: 100%;

@media (min-width: 728px){
.ds-advent-4 .et_pb_newsletter_form p {
margin-right: 1% !important;}

.et_pb_newsletter .et_pb_newsletter_fields>* {
flex-basis: 31% !important;}

@media (max-width: 727px) {
.et_pb_newsletter .et_pb_newsletter_fields>* {
flex-basis: 100% !important;}

.et_pb_newsletter_form input[type=password], .et_pb_newsletter_form input[type=text], .et_pb_newsletter_form p.et_pb_newsletter_field input[type=text], .et_pb_newsletter_form p.et_pb_newsletter_field textarea, .et_pb_newsletter_form select, .et_pb_newsletter_form textarea {
padding-left: 3.5em !important;