When Assets for InDesign is used in InDesign Server, the Assets Server credentials need to be passed as arguments in the start-up command of InDesign Server as part of the log in process.
This should look as follows:
InDesignServer -port <port_number> -elvisserver "<elvis_server_url" -elvisusername "<elvis_username>" -elvispassword "<elvis_password>"
A sample start-up command is:
InDesignServer -port 18383 -elvisserver "http://elvis.woodwing.net" -elvisusername "username" -elvispassword "password"
To see if the log in to Assets was successful, verify the console.