These AT commands are how the board communicates with the GSM modem. It seems that the board is using the primary COM port for this communication, and you are also trying to debug the Blynk connection via the same port. This results in nonsense data in your serial monitor, but it also results in your GSM modem seeing commands that it doesn’t understand, like “[10040] Connected to GPRS”.
You need to remove the #define BLYNK_PRINT Serial line of code from your sketch, and any additional lines of debug code that you might have added.
For more info about serial communication of this type, and how you can debug via a different COM port or software COM port you should read this…
Pete.