I'm converting from Blynk 0 to Blynk 2.0 and I can't get the data from a button to the hardware

I’m converting from Blynk 0 to Blynk 2.0 and I’m having many problems on the way. But now I’m at the state that only the data transfer from an mobile App to the hardware don’t work.
I’m a odd bird: I use Python 3, MS VS Code and Raspberry Pi 4.
But it worked fine with Blynk 0…
I’m now using the BlynkLib.py version = “1.0.0”.
I have tried every example showing how to get the data from the mobile App to the hardware firmware and it doesn’t work!!
Can some one please show me an example that works and also which has the way of fetching the data to a variable in an understandable way…

I have no other issues, only this: how to control my hardware from the mobile app. The other way it works fine.

A random example which doesn’t work for me:

import BlynkLib

BLYNK_AUTH = 'YourAuthToken'

# Initialize Blynk
blynk = BlynkLib.Blynk(BLYNK_AUTH)

# Register virtual pin handler
def v3_write_handler(value):
    print('Current slider value: {}'.format(value[0]))

while True: