Possible problems:
  • After moving Magento or the database to another server, payments fail, or 
  • the payment status in Magento is not updated correctly.

Cause #1:
If the error "SHA mismatch" appears in the Ingenico backend, all values that are stored encrypted need to be re-entered and saved in the Magento backend. For the Ingenico module, this affects:
  • SHA-IN 
  • SHA-OUT 
  • Password for the API-User 
The reason is the changed Encryption Key of Magento. This key changes when moving to another server, and therefore the saved values cannot be read correctly anymore.

Cause #2:
Maybe the IP addresses or the User Agent from Ingenico are blocked in the server environment (Firewall, Fail2Ban, etc.). The serverlogs should provide more information about this.

The IP addresses and the User Agent can be taken from Ingenico's technical documentation.

Cause #3:
The transaction feedback-URLs in the Ingenico backend have not been updated. You can find a detailled tutorial in this article.