Subject: Flex API Microform – “Invalid field - value” for card number in sandbox (2025)

[avalynn]

Hi everyone,

We are integrating CyberSource Flex API with Microform v2 in our Node.js checkout.

Card fields load correctly, tokenization call is made, but we always receive:

{
"response": {
"rm sg": "Invalid field - value",
" r c ode": "E100",
"details": [{"field": "ca r d _num b er", "message": "Invalid field - value"}]
}
}

What we’re using:

• Flex API key generated from sandbox Business Center (2025)
• Microform v2 latest script
• Test card: 4111111111111111, exp 12/2030, any CVV
• Capture context created with card_number, card_expirationMonth, card_expirationYear, card_type in fields array

Things already checked:

• Key has “Flex” permission enabled
• No extra spaces or hidden characters
• Tried both testrest and our own sandbox merchant ID
• Same error in Postman collection and live site

Question: Are the classic test cards (4111…, 5555…) still valid in sandbox in 2025, or did CyberSource update the test card list? If yes, could someone share the current working test card numbers for Microform tokenization?

Thanks a lot!

Luxshine Hair Team Hanoi, Vietnam

[aurden_amily]

It looks like your setup is correct, so the issue is likely on the sandbox side. CyberSource has been updating parts of the Flex and Microform stack, and some older test card patterns are no longer accepted for tokenization, even though they still work for other API tests. The “Invalid field – value” message usually points to the card number failing validation before token creation.

A few things to try that have worked for other teams recently:

– Use 4444333322221111 for Visa and 5431111111111111 for Mastercard. These have been accepted by the newer sandbox checks.
– Make sure the capture context includes exactly the expected field names from the latest Flex documentation. Even a small mismatch can trigger this error.
– Regenerate a fresh Flex key and capture context to clear any cached configuration.
– If you are loading Microform in an iframe, confirm that the script is the most recent version from the CyberSource CDN.

If these test cards work, then the 4111 card is no longer supported for tokenization in the updated sandbox.