Hi Ravi,
When you run F5 device related server tasks in SCOM, you need to have an appropriate device configuration token created (or cached) for the specific device, in order to have a successful task run. This behavior ties into the "Authorization Roles and Groups" model of the F5 Management Pack, i.e. supporting various authorization roles and groups via Microsoft SCOM, Active Directory, and F5 BIG-IP’s user authentication model. The F5 Management Pack includes built-in roles for discovery and device configuration and Microsoft Windows and Active Directory accounts can be correlated with BIG-IP user accounts via a one time device authentication (performed through an F5 Management Pack server task action).
In other words, prior to run any configuration related server task against an F5 device (such as Rediscovery, Enable/Disable LTM Virtual Server, Enable/Disable LTM Pool Member, etc.) you have to make sure you have a valid device configuration token. This is accomplished by running the "Set F5 Device Configuration Token" server task (right click on the F5 Device > F5 Device Tasks > Set F5 Device Configuration Token), where you'll need to provide your device authentication credentials for the appropriate overrides (see attached screen capture). These credentials will be mapped to the account running the server task(s), making up a 'device configuration token'. This is a one-time deal and you don't have to set the device configuration token with every server-task run, assuming you will use the same (Windows/Active Directory) account running the server task(s). If the device configuration token has been set up successfully, you should get an output similar to the screen capture attached (set-device-config-token-success.jpg) at the end of the set-device configuration task run.
Julian