Wanted to reply to imkingdavid as this helped me solve my issue. I had modified a core wordpress file to add a meta tag, assuming it would be displayed on all of the frontend pages. It appended my <meta keywords= tag to be beginning of the POST being made to admin-ajax.php, and therefore was no longer valid JSON data, and would not parse properly. I also went in the Chrome Network tab and looked at the response I got from the POST to admin-ajax.php and saw it hiding out there. I reverted my change and it fixed the issue!
