The error «unknown order/1/s/» means that the value of the SHASign parameter that you sent us in the hidden HTML fields for the transaction does not match the value that we calculated at our end.
The most common errors are:
- case mismatch in PSPID;
- incorrect SHA-1-IN signature.
The SHA-1-IN Signature field can be found in the “Data and origin verification” tab, “Checks for e-Commerce” section of the Technical Information page in your account.
Please note that the SHASign parameter counts as a secure digital signature and must be dynamically generated for each transaction.
For more information on SHA-1, please refer to the Advanced e-Commerce Integration Guide.
See also another explanation here: https://e-payment-postfinance.v-psp.com/en/en/guides/integration%20guides/possible-errors