Chris,
I just tried to login, and I'm seeing the following Facebook API Error at the top of the page:
Protocol https not supported or disabled in libcurl
It sounds like there's been a configuration change on your server where outgoing SSL connections are no longer possible. You'll need to investigate what change with PHP and, essentially, re-enable the SSL functionality for cURL which is required for proper operation.
If you need more information or help, just let us know!
Thanks,
Alex