is it UCCE?
are you trying to login an mobile agent?
some info:
This issue can occur if the Unified MA has entered an invalid Instrument ID. For example, the issue can occur when the Instrument ID of a valid IP Phone (Non-LCP) was entered. You must verify that the agent uses the correct LCP.
If the Unified MA does not check the Mobile Agent checkbox and attempts to log in with their agent credentials and LCP Instrument ID, then this error is received. Ensure that Unified MAs have the Mobile Agent check box checked.
regards
Chintan