Social media plays a big role in employer branding, so you might want to add your social medias to your career site in the social widget. This allows your potential candidates to keep up to date with your social accounts.
However, if you can't seem to get the Facebook page to work it might be because you have an age or country restriction on your page. You need to have a fully accessible page for the integration to work.
Have a look here to see how to edit your FB page's restrictions: https://www.facebook.com/help/778445532225441