Is it licensing? If you're in an evaluation, you likely have a trial license, which normally includes 10 licenses. You could be out of licenses. Have you checked Symantec Installation Manager on the Notification Server to see how many licenses are available for Inventory Solution? Basic inventory doesn't require a license, so this would fit with the licensing theory.
If you need a larger amount of trial licenses, you should contact your sales rep.
Does this help?