You can enable debug by use :
#define BLYNK_DEBUG // Optional, this enables lots of prints
#define BLYNK_PRINT Serial
Verify all this points :
If you experience connection problems, follow these steps:
Check that your hardware, wires, cables and power supply are good quality, not harmed or damaged, etc.
Use high power USB cables and USB ports.
Check your wiring using the examples (TCP/HTTP Client or similar) provided with your shield and hardware.
Once you understand how to manage connection, it’s much easier to use Blynk.
Try running command telnet blynk-cloud.com 8442 from your PC, connected to the same network as your hardware. You should see something like: Connected to blynk-cloud.com..
Try running Blynk default examples for your platform without modifications to see if it is working.
Double-check that you have selected the right example for your connection type and hardware model.
Our examples come with comments and explanations. Read them carefully.
Check that your Auth Token is valid (copied from the App and doesn’t contain spaces, etc.)
If it doesn’t work, try looking into serial debug prints.
Done! Add your modifications and functionality. Enjoy Blynk!
Note: when you have multiple devices connected to your network, they should all have different MAC and IP addresses. For example, when using 2 Arduino UNO with Ethernet shields, flashing default example to both of them will cause connection problems. You should use manual ethernet configuration example.
WiFi network connection
If you encounter WiFi connection problems, please check these pitfalls:
You’re trying to connect to “WPA & WPA2 Enterprise” network (often used in offices), and your shield does not support this security method
Your WiFi network has a login page that requests entering an access token (often used in restaurants)
Your WiFi network security disallows connecting alien devices completely (MAC filtering, etc)
There is a firewall running. Default port for hardware connections is 8442. Make sure it’s open.
Can you paste your code here and give your GATEWAY. I think is a problem with your network.