Omnipay Postfinance issues error messages

[Rocco]

My configuration:
_ Typo3 10.4.19
_ aimeos/aimeos-typo3 21.7.2
_ aimeos/ai-payments 21.7
_bummzack/omnipay-postfinance @dev

When paying with Postfinance, I get the following error on https://e-payment.postfinance.ch/ncol/t ... andard.asp:
Payment confirmation
Order reference : 1
Total charge : ---
Beneficiary : ---

I find the following log entry in the PostFinance back office:
Datum time: 2021-08-26 10:25:43
Modus: STD
Anforderung: 178.38.110.214
Bezahlung ID: 0
ORDERID: 1
Beschreibung: unknown order/1/s/

My configuration in the Aimeos backend looks like this:
Dienstanbieter: Omnipay
address: yes
authorize: yes
createtoken: no
onsite: no
pspId: "xxxxTest"
shaIn: "the code from Postfinance"
shaOut: "the code from Postfinance"
testmode: yes

Does anyone have any idea why this isn't working?
Thank you for any help.

[aimeos]

Seems like an invalid hash:
https://docs.openstream.ch/payment-prov ... -messages/