ERROR: "Callback failure: no result received from callback [validateOS]..." (4261208)

SQL Server database agent installer wizard fails with the following error:

Monitoring <hostname> Initialized Failed
Error: OS Validation failed

Suggestions:
Re-run the agent installation wizard. If the issues persists, contact Quest Support

Details:
Callback failure: no result received from callback [validateOS] on agent DBSS-Installer-<hostname>, session <sessionID>, request <requestID>

CAUSE 1

Timeout issue

CAUSE 2

Deactivated or corrupt database installer agent

RESOLUTION 1

To increase the timeout, follow the steps below:

1. Go to "Administration | Agents | Agent Status"
2. Select the agent "DB_SQL_Server_Installer" and click on "Edit Properties" at the bottom of the page
3. Click on "Modify properties for this agent only"
4. Change the parameter "Windows Connection Timeout (milliseconds)" from 60000 to 180000
5. Click on "Save"

Now re-run the database agent installer wizard.

RESOLUTION 2

Navigate to Administration | Agent Status and confirm that the Database installer agent is activated. In some circumstances deleting the database installer agent and recreating it manually on the same agent manager (FglAM) can help this issue.