How are you connecting your Uno to your PC?
You’ve defined two separate serial ports - the hardware serial for the USB to Blynk connection and a software serial port on pins 10 and 11 for debug. To see this debug output you’ll need a TTL to USB adapter (an FTDI Adapter) connected to Pins 10 & 11 (don’t forget to cross Tx & Rx). This will give you an additional serial port that can be selected in your Arduino IDE and will show you the debug output.
Is this what you’re doing, and if so, what does the debug output say?
Also, you don’t make any mention of the USB script that needs to be running in an open terminal session on your PC (closing the session will kill the connection). Are you running this script?
Unfortunately, you’ve chosen one of the most difficult boards to work with, as it has no built-in internet connectivity (essential for an IoT system) and it only has one built-in serial port, which makes connection to a device that will give you internet connectivity more difficult.
Maybe you should read this and re-consider your choice of board:
Pete.