How to Detect Invalid PIN During Pairing?

I am testing BT pairing using CC2564B and Bluetopia SDK 1.4R2.

The problem I am facing is in detecting when user enters an invalid PIN during pairing. I am using an Android phone to pair the device. If I enter invalid PIN from the Android phone, the connection doesn't get established as expected, but I haven't been able to find a way to identify that the PIN was invalid.

Until today, I was relying on the return value of GAP_Authentication_Response() in PINCodeResponse() (see below) , but found out a few minutes ago that its return value is not actually an indication of valid/invalid PIN. Based on this post, I tried to use GAP_Event_Callback() case atAuthenticationStatus. But this doesn't get called for some reason. Please let me know the right way to detect invalid PIN entry.

int PINCodeResponse(ParameterList_t *TempParam)
{
   int                              Result;
   int                              ret_val;
   PIN_Code_t                       PINCode;
   GAP_Authentication_Information_t GAP_Authentication_Information;

   /* First, check that valid Bluetooth Stack ID exists.                */
   if(BluetoothStackID)
   {
      /* First, check to see if there is an on-going Pairing operation  */
      /* active.                                                        */
      if(!COMPARE_BD_ADDR(CurrentRemoteBD_ADDR, NullADDR))
      {
         /* Make sure that all of the parameters required for this      */
         /* function appear to be at least semi-valid.                  */
         if((TempParam) && (TempParam->NumberofParameters > 0) && (TempParam->Params[0].strParam) && (BTPS_StringLength(TempParam->Params[0].strParam) > 0) && (BTPS_StringLength(TempParam->Params[0].strParam) <= sizeof(PIN_Code_t)))
         {
            /* Parameters appear to be valid, go ahead and convert the  */
            /* input parameter into a PIN Code.                         */

            /* Initialize the PIN code.                                 */
            ASSIGN_PIN_CODE(PINCode, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);

            BTPS_MemCopy(&PINCode, TempParam->Params[0].strParam, BTPS_StringLength(TempParam->Params[0].strParam));

            /* Populate the response structure.                         */
            GAP_Authentication_Information.GAP_Authentication_Type      = atPINCode;
            GAP_Authentication_Information.Authentication_Data_Length   = (Byte_t)(BTPS_StringLength(TempParam->Params[0].strParam));
            GAP_Authentication_Information.Authentication_Data.PIN_Code = PINCode;

            /* Submit the Authentication Response.                      */
            Result = GAP_Authentication_Response(BluetoothStackID, CurrentRemoteBD_ADDR, &GAP_Authentication_Information);

            /* Check the return value for the submitted command for     */
            /* success.                                                 */
            if(!Result)
            {
               /* Flag success to the caller.                           */
               ret_val = 0;
            }
            else
            {
            	ret_val = FUNCTION_ERROR;
            }

            /* Flag that there is no longer a current Authentication    */
            /* procedure in progress.                                   */
            ASSIGN_BD_ADDR(CurrentRemoteBD_ADDR, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00);
         }
         else
         {
            ret_val = INVALID_PARAMETERS_ERROR;
         }
      }
      else
      {
         ret_val = FUNCTION_ERROR;
      }
   }
   else
   {
      /* No valid Bluetooth Stack ID exists.                            */
      ret_val = INVALID_STACK_ID_ERROR;
   }

   return(ret_val);
}

Excerpts from GAP_Event_Callback():

static void BTPSAPI GAP_Event_Callback(unsigned int BluetoothStackID, GAP_Event_Data_t *GAP_Event_Data, unsigned long CallbackParameter)
{
    int                               Result;
    int                               Index;
    BD_ADDR_t                         NULL_BD_ADDR;
    Boolean_t						 OOB_Data;
    Boolean_t                         MITM;
    GAP_IO_Capability_t               RemoteIOCapability;
    GAP_Inquiry_Event_Data_t         *GAP_Inquiry_Event_Data;
    GAP_Remote_Name_Event_Data_t     *GAP_Remote_Name_Event_Data;
    GAP_Authentication_Information_t  GAP_Authentication_Information;

    /* First, check to see if the required parameters appear to be       */
    /* semi-valid.                                                       */
    if ((BluetoothStackID) && (GAP_Event_Data))
    {
        /* The parameters appear to be semi-valid, now check to see what  */
        /* type the incoming event is.                                    */
        switch (GAP_Event_Data->Event_Data_Type)
        {
        case etInquiry_Result:
            break;

        case etInquiry_Entry_Result:
            break;

        case etAuthentication:
            /* An authentication event occurred, determine which type of*/
            /* authentication event occurred.                           */
            switch (GAP_Event_Data->Event_Data.GAP_Authentication_Event_Data->GAP_Authentication_Event_Type)
            {
            case atLinkKeyRequest:
                break;

            case atPINCodeRequest:
                break;

            case atAuthenticationStatus:
                /* An authentication status event occurred, display   */
                /* all relevant information.                          */
                BD_ADDRToStr(GAP_Event_Data->Event_Data.GAP_Authentication_Event_Data->Remote_Device, Callback_BoardStr);
                /* Flag that there is no longer a current             */
                /* Authentication procedure in progress.              */
                ASSIGN_BD_ADDR(CurrentRemoteBD_ADDR, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00);
                break;

            case atLinkKeyCreation:
                break;

            case atIOCapabilityRequest:
                break;

            case atIOCapabilityResponse:
                break;

            case atUserConfirmationRequest:
                break;

            case atPasskeyRequest:
                break;

            case atRemoteOutOfBandDataRequest:
                break;

            case atPasskeyNotification:
                break;

            case atKeypressNotification:
                break;

            default:
                break;
            }
            break;

        case etRemote_Name_Result:
            break;

        case etEncryption_Change_Result:
            break;

        default:
            break;
        }
    }
}