One of the reason can be, during discovery of the device the probing was unsuccessful due to ASNMP error and the device was added to the pending list. This entry was added in the pending list due to FAIL_PROBE error in the ic-mib2-hyper-data.asl file.
You can confirm that by looking into the "Description" field in the "Pending List(AD_PendingData)".
In this case the "Description" will have one of the following or both the error messages:
"ASNM-E-ASNMP_SEND_RECEIVE_ERROR-ASNMP request failure: Error when sending or receiving SNMP data for Host '<IP address of the device>' (Maybe bad credentials)."
"ASNM-E-ASNMP_SNMP_ERROR-ASNMP request failure: Error <Error Code>: <Error Message> when receiving SNMP Packet from '<IP address of the device, port<port number>'"
