Now the HTML element contains the "disabled" attribute, which is interpreted by browser as disabled state independently of it's value.
<input id="agree" class="field" data-field-name="termsandconditions" data-field-type="text" disabled="" type="checkbox">
So, the only way to check this box on is to edit element through HTML debugging tools to make it NOT disabled. The "disabled" HTML attribute should be never used on enabled <input> element
