Being able to talk directly to the Blynk server via MQTT is quite a new facility, and one that I’ve not done very much testing with, other than when it was first released.
Prior to that, the only method of using Node-Red with Blynk was via the Blynk contrib, and later the Blynk IoT contrib (when the current Blynk IoT product was released).
As I’ve always used this method to communicate with Blynk, it’s what I still use - because it’s simple and straightforward and works very well.
How to use the Blynk IoT contrib is covered in this topic…
Pay attention to which nodes to use when receiving data and sending data, as the naming isn’t exactly intuitive.
Also, don’t try mixing flows using direct MQTT communication and the Blynk IoT contrib, as you may get conflicts caused by attempting to use the same Auth token at the same time.
Pete.