Checkboxes Not Displaying

For some reason your theme decided to block all inputs out for Chrome and Safari (webkit):

[css]
input, textarea, button {
outline: none!important;
background: none;
border-radius: 0;
box-shadow: none!important;
-webkit-appearance: none!important;
}

Just place this CSS snippet in your theme's stylesheet (or wherever you are instructed to place custom CSS at the theme level).

[css]
.gform_wrapper ul.gfield_checkbox li input[type=checkbox] {
-webkit-appearance: checkbox!important;
}
.gform_wrapper ul.gfield_radio li input[type=radio] {
-webkit-appearance: radio!important;
}