Problem with action that should happen in loop(continuously)
The BLYNK_WRITE(V1) function is only called when a Blynk app widget sends data to your hardware. It does not run in a loop. If you want something to run in a loop, put it in loop().

The WRITE aspect is from the point of view of the App, not of your hardware, so your hardware uses BLYNK_WRITE() to receive information from the app. And it's only called when the app chooses to send that information. For example, when a button in the Blynk smartphone app is pushed.