In WW 2.18 when a mass grade update runs/fails - there should be a log record. See the
$job->app->log
calls inĀ https://github.com/openwebwork/webwork2/blob/main/lib/Mojolicious/WeBWorK/Tasks/LTIMassUpdate.pm Until WW 2.17 - only when the
$debug_lti_grade_passback
was turned on would there be any logging.