No idea what it does... but just did some googling for opther mqtt code and found that the setserver line on line 349 is being converted using the cvhar command whereas it can just be put in inside brackets... changed it from
char *mqtt_server = &config.mqttserver[0u]; //Convert the server string to char array for mqtt client
MQTTClient.setServer(mqtt_server, 1883);
to
MQTTClient.setServer("192.168.0.116", 1883);
and now it connects and subscribed...