Why this email input field with a required attribute fail W3C validation? (html5 page)

Trying to fix 2 errors when validating a contact page that I am working on. It does have a at the top of the page as inputs with required need to be in html5 pages.

Here is the W3C Link to the results.

Code in question:

<input class="input-box form-control" type="email" placeholder="Email" id="email" name="email" value="" data-error="Please add a valid email address." required>

Any help or guidance would be appreciated :) Thanks!