What does Error Code 4019 mean?

Error code 4019: The e-commerce indicator for the transaction is not allowed on your application.

Here are what each ECI indicator means:

VISA:

• ECI 5 - Fully 3D secure (cardholder enters their OTP) 
• ECI 6 - Cardholder not enrolled for 3D secure 
• ECI 7 - Undefined card (Banks deem these transactions as possible fraudulent transactions)

Mastercard

• ECI 2 - Fully 3D secure (cardholder enters their OTP) 
• ECI 1 - Cardholder not enrolled for 3D secure 
• ECI 7 - Undefined card (Banks deem these transactions as possible fraudulent transactions)