A popup with the message "Failed to invoke agent callback" appears when adding a new SQL Server database agent.
The SQL Server database agent installer has calls to some code that invokes the installer agent several times and then errors out.
RESOLUTION #1 * This is the most common resolution *
Restart the FMS and the Agent Manager.
Review the sizing of the number of agents on the FMS, particularly the FglAM involved and the total sizing of DB2 agents if present on the system.