Does the actual baudrate on the ESP and the Arduino serial port match? Some ESP’s are out of the box with a setting of 9600, others 115200 and so on. You could check by hooking up the ESP to a USB-Serial convertor and see when it connects to it properly and responds with OK to an AT command.
I set baud rate on ESP8266 to 9600, then it responsed OK with command AT. In an other hand, I also tested with Arduino UNO, use software serial in above code but Blynk app show your “Arduino UNO is not in network”.
You are right! The first problem which newbies as me usually get is ignoring vendor’s official guide.
From above captured serial monitor, I see that my ESP got an incorrect IP address from DHCP although serial monitor shown “connected to wifi”. It has to be 192.168.0.X as my router. Thus, ESP did not connect exactly to router. After checking AT commands, I revealed that I have to set ESP to client mode and disable it’s DHCP.
Finally, the command helped me having motivation with ESP8266:
Thank you for your information - in fact I still use the old libraries and luckily work it. I only hope that it will work until the “end of the world” because some of the systems I gave my colleagues and me will be difficult to update them.