"Cronmanager encountered 1 Errors"

Hi, I had a freepbx ran great, but suddenly I saw this message:

“Cronmanager encountered 1 Errors
The following commands failed with the listed error
/var/lib/asterisk/bin/module_admin listonline (255)
Added 19 hours, 37 minutes ago
(cron_manager.EXECFAIL)”

So, how do I correct the error?

Thanks.
Roger