Thanks for all the help. I have not been able to rework the code yet, but I will take that as a working thesis and consider this problem closed. I really appreciate your help and patience as I work my way through this.

@jkandasa,
I also looked at my logs, and mostly they say this:

statusSince=1515091216204, txDelay=0), driver=AUTO, portName=/dev/ttyUSB0, baudRate=115200, retryFrequency=60, runningDriver=JSERIALCOMM)], Unable to reconnected! Will do next try after 60 second(s)
2018-01-05 05:13:09,374 INFO [Thread-32] [org.mycontroller.standalone.gateway.serialport.SerialPortMonitoringThread:112] Serial GatewayTable[GatewaySerial(super=Gateway(id=2, enabled=true, name=Home, type=SERIAL, networkType=MY_SENSORS, timestamp=1515091215685, state=DOWN, statusMessage=ERROR: Unable to open!, statusSince=1515091216204, txDelay=0), driver=AUTO, portName=/dev/ttyUSB0, baudRate=115200, retryFrequency=60, runningDriver=JSERIALCOMM)] not connected, Reconnect initiated...
2018-01-05 05:13:09,886 ERROR [Thread-32] [org.mycontroller.standalone.gateway.serialport.SerialPortjSerialCommImpl:74] Unable to open serial port:[/dev/ttyUSB0]
2018-01-05 05:13:09,894 INFO [Thread-32] [org.mycontroller.standalone.gateway.serialport.SerialPortMonitoringThread:93] Serial GatewayTable[GatewaySerial(super=Gateway(id=2, enabled=true, name=Home, type=SERIAL, networkType=MY_SENSORS, timestamp=1515091215685, state=DOWN, statusMessage=ERROR: Unable to open!, statusSince=1515091216204, txDelay=0), driver=AUTO, portName=/dev/ttyUSB0, baudRate=115200, retryFrequency=60, runningDriver=JSERIALCOMM)], Unable to reconnected! Will do next try after 60 second(s)

@jkandasa,
Sorry it took so long to get back to you. Here is my configuration screenshot:

And here is my gateway sketch:

/**
* The MySensors Arduino library handles the wireless radio link and protocol
* between your home built sensors/actuators and HA controller of choice.
* The sensors forms a self healing radio network with optional repeaters. Each
* repeater and gateway builds a routing tables in EEPROM which keeps track of the
* network topology allowing messages to be routed to nodes.
*
* Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
* Copyright (C) 2013-2015 Sensnology AB
* Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
*
* Documentation: http://www.mysensors.org
* Support Forum: http://forum.mysensors.org
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* version 2 as published by the Free Software Foundation.
*
*******************************
*
* DESCRIPTION
* The ArduinoGateway prints data received from sensors on the serial link.
* The gateway accepts input on seral which will be sent out on radio network.
*
* The GW code is designed for Arduino Nano 328p / 16MHz
*
* Wire connections (OPTIONAL):
* - Inclusion button should be connected between digital pin 3 and GND
* - RX/TX/ERR leds need to be connected between +5V (anode) and digital pin 6/5/4 with resistor 270-330R in a series
*
* LEDs (OPTIONAL):
* - To use the feature, uncomment any of the MY_DEFAULT_xx_LED_PINs
* - RX (green) - blink fast on radio message recieved. In inclusion mode will blink fast only on presentation recieved
* - TX (yellow) - blink fast on radio message transmitted. In inclusion mode will blink slowly
* - ERR (red) - fast blink on error during transmission error or recieve crc error
*
* Samuel Mills uptated this version for his personal use.
*/

// Enable debug prints to serial monitor
#define MY_DEBUG


// Enable and select radio type attached
#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69

// Set LOW transmit power level as default, if you have an amplified NRF-module and
// power your radio separately with a good regulator you can turn up PA level.
#define MY_RF24_PA_LEVEL RF24_PA_LOW

// Enable serial gateway
#define MY_GATEWAY_SERIAL

// Define a lower baud rate for Arduino's running on 8 MHz (Arduino Pro Mini 3.3V & SenseBender)
#if F_CPU == 8000000L
#define MY_BAUD_RATE 38400
#endif

// Enable inclusion mode
#define MY_INCLUSION_MODE_FEATURE
// Enable Inclusion mode button on gateway
#define MY_INCLUSION_BUTTON_FEATURE

// Inverses behavior of inclusion button (if using external pullup)
//#define MY_INCLUSION_BUTTON_EXTERNAL_PULLUP

// Set inclusion mode duration (in seconds)
#define MY_INCLUSION_MODE_DURATION 60
// Digital pin used for inclusion mode button
#define MY_INCLUSION_MODE_BUTTON_PIN  7

// Set blinking period
#define MY_DEFAULT_LED_BLINK_PERIOD 1000

// Inverses the behavior of leds
#define MY_WITH_LEDS_BLINKING_INVERSE

// Flash leds on rx/tx/err
// Uncomment to override default HW configurations
#define MY_DEFAULT_ERR_LED_PIN 4  // Error led pin
#define MY_DEFAULT_RX_LED_PIN  6  // Receive led pin
#define MY_DEFAULT_TX_LED_PIN  5  // the PCB, on board LED

#include <MySensors.h>
#include <DHT.h>
const int DHTPin = 3;
static const uint64_t Update_Interval = 60000;
#define CHILD_ID_HUM 0
#define CHILD_ID_TEMP 1
#define SENSOR_TEMP_OFFSET 0
float lastTemp;
float lastHum;
uint8_t nNoUpdatesTemp;
uint8_t nNoUpdatesHum;
bool metric = true;
static const uint8_t FORCE_UPDATE_N_READS = 30;
static const uint64_t UPDATE_INTERVAL = 60000;
MyMessage msgHum(CHILD_ID_HUM, V_HUM);
MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);
DHT dht(3, DHT11);

void setup()
{
  pinMode(3, INPUT_PULLUP);
  pinMode(7, INPUT_PULLUP);
  sleep(500);
	// Setup locally attached sensors
}

void presentation()
{
	present(CHILD_ID_HUM, S_HUM);
  present(CHILD_ID_TEMP, S_TEMP);
  metric = getConfig().isMetric;
	
	// Present locally attached sensors
}

void loop()
{
	 // Force reading sensor, so it works also after sleep()
  dht.readTemperature();
  dht.readHumidity();

  // Get temperature from DHT library
  float temperature = dht.readTemperature();
  if (isnan(temperature)) {
    Serial.println("Failed reading temperature from DHT!");
  } else if (temperature != lastTemp || nNoUpdatesTemp == FORCE_UPDATE_N_READS) {
    // Only send temperature if it changed since the last measurement or if we didn't send an update for n times
    lastTemp = temperature;
   if (!metric) {
      temperature = dht.readTemperature(true);
    }
   
    // Reset no updates counter
    nNoUpdatesTemp = 0;
    temperature += SENSOR_TEMP_OFFSET;
    send(msgTemp.set(temperature, 1));

    #ifdef MY_DEBUG
    Serial.print("T: ");
    Serial.println(temperature);
    #endif
  } else {
    // Increase no update counter if the temperature stayed the same
    nNoUpdatesTemp++;
  }

  // Get humidity from DHT library
  float humidity = dht.readHumidity();
  if (isnan(humidity)) {
    Serial.println("Failed reading humidity from DHT");
  } else if (humidity != lastHum || nNoUpdatesHum == FORCE_UPDATE_N_READS) {
    // Only send humidity if it changed since the last measurement or if we didn't send an update for n times
    lastHum = humidity;
    // Reset no updates counter
    nNoUpdatesHum = 0;
    send(msgHum.set(humidity, 1));

    #ifdef MY_DEBUG
    Serial.print("H: ");
    Serial.println(humidity);
    #endif
  } else {
    // Increase no update counter if the humidity stayed the same
    nNoUpdatesHum++;
  }

  // Sleep for a while to save energy
  sleep(UPDATE_INTERVAL);
	// Send locally attached sensor data here
}```

@jkandasa. Thank you for taking the time to help. I am using the USB-TTL connection to my gateway.

Hello,
I am running mycontroller on an RPI3 with a serial gateway. My gateway includes a DTH11 sensor. My second node contains a DTH11 and BMP 280. My nodes communicate via NRF24L01+. When I view the gateway node via the serial monitor in the Arduino IDE (or putty), I can see values from both nodes, and all sensors. I also get a green Rx light on my gateway with every expected Tx of my second node. When I launch mycontroller "sudo ./start.sh" and log in with a web browser, my gateway and first node show green on the topology graphic. I do not receive any values from the DTH11, and there is no indication of my second node. After about 10 minutes, my first node appears dead to the controller. I have deleted and re-installed my gateway to no avail. I have also completed the troubleshooting under the thread "Frustrated Newbie" and after reconnecting my gateway, the auto detect found the first node, and one sensor, but not the second node or all sensors. Please help me correct this issue.

Thank you all for the help. I added my user to the tty group and was able to connect to my gateway.

I have deleted and re-installed the gateway with the correct port name.
I also ran the command you requested and returned this result:
crw-re---- 1 root dialout 188, 0 Jan 4 06:26 /dev/ttyUSB0

Thanks for the help

Yes, that was a typo, unfortunately it did not fix the problem.

I have installed MyController on a Raspberry Pi 3 and have built a serial gateway with an Arduino Nano and uploaded the example sketch. Based on the serial monitor output read in the Arduino IDE, the gateway is working, and receiving data from my other sensor. When I attempt to add a controller from the MyController resources page, I get "Error: Unable to open!" for the status message. Under connection details, I have listed
"Port:/dev/tty/USB0, BaudRate:115200, Driver:Auto[jSerialComm], RetryFrequency:60 Second(s)"

I have selected each of the driver options, but they give me worse (and more clear) status messages.

Any ideas on how to over come this issue?

Thanks