Steps to reproduce the issue

Log into Joomla with regular login credentials: email and password (accesses by typing administrator at the end of website url)

Expected result

Successfully logged in, showing normal admin interface with current, up to date content (articles, media, items, etc)

Actual result

Login error
Use of undefined constant JAUTHENTICATE_STATUS_FAILURE - assumed 'JAUTHENTICATE_STATUS_FAILURE' (this will throw an Error in a future version of PHP) in /home/forge/www.cg-la.com/plugins/authentication/facebook/facebook.php on line 98
Says user and password do not match or you don’t have an account yet.
Had to get access again by creating an admin account again, only to see when logged into admin interface that everything past January 2019 has been deleted (modules, items, articles, media, etc.)

System information (as much as possible)

Additional comments

Hosted by Cloudflare and Amazon Web Services, tried to reboot server through Media Temple but still shows the old website. Trying to figure out how I can restore it back to where it was and whether or not this is fixable through Joomla/caused by Joomla?