Plugin could not be activated because it triggered a fatal error.

Plugin could not be activated because it triggered a fatal error.

Parse error: syntax error, unexpected ‘[‘ in [site]/wp-content/plugins/wp-scheduled-posts/includes/class-wpsp-helper.php on line 21

All I did was update the plugin and began receiving this fatal error (Had to edit code directly to clear error). Uninstalled plugin and then reinstalled it and got the same error as a warning preventing the plugin from being activated.