Keep the receive section clean - I took all the 'if' and 'elseif' out of receive and into the main loop - This is good practice. So now it looks like this......

// process incoming message
void receive(const MyMessage &message) {
  if (message.sensor == CHILD_ID_GETFORECAST && message.type == V_FORECAST) {
    forecast = (message.getString());
    NewForecast = 1;
  }
}

The NewForecast is there to alert the main loop to a new incomming value to be tested and updated.

Thanks I got it to work!

The below is what I used as I cannot display the full message on a small oled and so I use abbreviations held in an array. Therefore I needed to get a value to act as a pointer to the message to display and the below did the trick! - Node finished!

void receive(const MyMessage &message) {
   if (message.sensor == CHILD_ID_GETFORECAST && message.type == V_FORECAST) {
    forecast = (message.getString());
    if (forecast == "stable"){
    Index = 0;}
    else if (forecast == "sunny"){
    Index = 1;}
    else if (forecast == "cloudy"){
    Index = 2;}
    else if (forecast == "unstable"){
    Index = 3;}
    else if (forecast == "thunderstorm"){
    Index = 4;}
    else if (forecast == "unknown"){
    Index = 5;}
 
  }

I do not know what that is - is it an int? byte?string?

MyController receives all the payload in String format and sends all the payload in String format.
From the gateway, MyController receives payload as String, https://www.mysensors.org/download/serial_api_20
However, We have multiple functions in MySensors, based on your payload you can call a particular function,
https://www.mysensors.org/download/sensor_api_20#message-constructor

 // Getters for picking up payload on incoming messages
    char* getStream(char *buffer) const;
    char* getString(char *buffer) const;
    const char* getString() const;
    void* getCustom() const;
    uint8_t getByte() const;
    bool getBool() const;
    float getFloat() const;
    long getLong() const;
    unsigned long getULong() const;
    int getInt() const;
    unsigned int getUInt() const;

Can you check it in the resources page, do you receive data from the source node? You can enable Notice and check activities in resources log page.

@skywatch MyController sends payload as is.

I do not know what that is - is it an int? byte?string?

Can you double check that, you have configured right sensor?

Yes I have, I can send the receiving node a byte and the screen displays the correct value. I did this to test with action>send raw message and it was good.

You may debug by adding a serial print line right after void receive(const MyMessage &message) { before if loop?

That's a thought for tomorrow.....thanks!

I think I have the wrong variable type to get V_FORECAST - Although I only need a byte or int with the index pointer of the current forecast (0-5).

When testing it with byte received I could send a raw message and it worked, so I guess it is not a byte or int that is sent to the controller and then on to the node?