Have you tried reading what it says on the GitHub page for the PZEM004Tv30.h library and looking at the examples there?
When you read things like this…
but then don’t use the ESP8266 example as the basis for your PZEM portion of the sketch then it’s not surprising that it doesn’t work.
I’d suggest that you get the PZEM portion of the sketch working first, and understand how it works, then add that working code into your Blynk sketch.
You should then search the forum for “keep your void loop clean” and understand how to use timers to call a function rather than placing everything in your void loop and using delays.
In other words…
Pete.