[Sandbox Smart Checkout] 502 Bad Gateway during 3DS challenge & payment flow

[Georgekalogerakis]

We are experiencing a consistent payment failure issue in the Viva Wallet Smart Checkout (sandbox environment).

The issue started suddenly since Saturday morning (28 Mar 2026) , with no changes on our side. Everything was working correctly before that.

Environment
Integration: Viva Smart Checkout (web2)
Environment: Sandbox
Example URL that is generated per session:
https://demo.vivapayments.com/web2?ref=xxxxxxxxxxxxxxxxx

1. 3DS Challenge Flow (Demo card with 3DS)

During the 3DS authentication step, instead of completing the challenge, the system returns:

502 Bad Gateway
nginx

This appears inside the embedded/payment iframe.

2. Non-3DS Cards (Demo cards)

Even when using demo cards that do NOT require 3DS, the payment still fails after clicking "Pay", showing:

Your payment could not be processed (you have not been charged).
Please retry or try a different payment method.

[Georgekalogerakis]

Problem seems solved by Viva's side today or yesterday.