[Plugin: WPCB] Incomplete transaction when paying with credit card

Payment by check or Paypal works fine. However when I pay with a credit card, I go through the bank portal sucessfully, the program brings me back to the home page as expected, but the basket does not empty and the transaction is reported as incomplete.
I tried both the test bank portal and the pre-production bank portal with no difference.

Any thought?

https://www.ads-software.com/extend/plugins/wpcb/