Probably because of the hugeness of the Wikimedia Phabricator, the Burnup Graph is timing out. It would be nice if it's functionality is restored. The error provided is:
>>> UNRECOVERABLE FATAL ERROR <<< Maximum execution time of 10 seconds exceeded /srv/deployment/phabricator/deployment/phabricator/src/applications/maniphest/constants/ManiphestTaskStatus.php:128