Common Redsys errors and how to fix them
What the most frequent Redsys codes mean — SIS0042, SIS0051, SIS0046, MasterCard 172/173/174 — and how to solve each.
Most Redsys errors come from wrong credentials or configuration. SIS0042 means the signature is wrong (check your secret key / SHA-256). SIS0051 means a duplicate order number. SIS0046 means the card BIN is not registered. MasterCard codes 172, 173 and 174 are mandatory-action codes that the Premium plugin handles automatically.
How to read a Redsys error
Redsys returns a code (often starting with SIS) when a transaction is rejected. The code tells you the cause; most are configuration, not card, problems.
Enable the plugin logs (Detailed Transaction Logs in Premium) to capture the exact code and the request that produced it.
Common error codes
These are the codes most stores see and what to do about each.
| Code | Meaning | How to fix |
|---|---|---|
| SIS0042 | The signature sent is not correct. | Re-copy the SHA-256 secret key exactly; confirm the plugin uses SHA-256, not an old algorithm. |
| SIS0051 | Duplicate order number. | A failed attempt keeps the order number reserved. Use a new, unique order number for each attempt. |
| SIS0046 | The card BIN is not registered. | Contact your bank or Redsys to register the card BIN or adjust your payment method configuration. |
| 172 / 173 / 174 | MasterCard mandatory-action codes. | The Premium plugin performs the required actions automatically — no configuration needed. |
MasterCard errors 172, 173 and 174
When MasterCard returns 172, 173 or 174, the merchant must perform mandatory actions or risk sanctions from MasterCard and restrictions from the bank.
The Premium plugin's MasterCard error control handles these automatically, with no setup — a risk most stores do not even know exists.
Troubleshooting checklist
- Confirm the three credentials — merchant code, terminal and secret key — match your bank exactly.
- Check the environment: test credentials only work in the test environment, live in live.
- Make sure the plugin uses SHA-256.
- Read the plugin logs for the exact SIS code.
- If it persists, contact support with the code and the log entry.
Frequently asked questions
José Conti provides premium payment gateway plugins completely free, with lifetime support, for legally registered nonprofit organizations. If you run a nonprofit and need to accept payments through Redsys, apply for a free license.
Stop losing payments to errors
Premium adds automatic MasterCard error control and detailed logs to diagnose any issue fast.