A possible reason for the error message is that the client name is already deleted from the database.
The exact message looks similar to this:
day month date time year [SECURITY] apf_ms.c 2670: Unable to delete usernamewirelessconnection for mobile 00:00:00:00:00:00
When you try to delete the user from the database entry of the WiSM you get this error message. Try one of the steps below
Refer to these documents for more information