There could be many reasons - was SYSADMIN delegation rule enabled ? or was SYSADMIN assigned to a HR User ?
Are you referring to error notifications?
Have you done any changes on the env recently? Any new patches?
How to handle or reassign System : Error (WFERROR) Notifications that default to SYSADMIN (Doc ID 1448095.1)
The issue is fixed as someone has assigned vacation rule for SYSADMIN
How do I close this close this discussion, as I cannot see any option.