connection error VS negativeCompletionReceived

[obelixA]

NuGet Package Version

2.17.0

Payment service provider

?

Payment terminal

Worldline

Communication Logs

No response

More information

on terminal, which do not need authentication my payment works fine (thanks to our conference call some weeks ago!!).
But now I was trying to start a payment on a device, which needs authentication first.
According to the documentation I added 3 lines of code (see below "INSERTED")
w/o this line of code I get the message "negativerCompletionReceived".
with these lines I get "connection error"

any ideas what goes wrong?

thanks in advance

using var zvtClient = new ZvtClient( _comm, clientConfig: clientConfig );
latestZvtClient = zvtClient;
zvtClient.StatusInformationReceived += ( statusInformation ) => OnLogit?.Invoke( statusInformation.ErrorMessage );
zvtClient.IntermediateStatusInformationReceived += ( msg ) => OnLogit?.Invoke( msg );
zvtClient.LineReceived += ( printLineInfo ) => OnLogit?.Invoke( printLineInfo.Text );
zvtClient.ReceiptReceived += ( receiptInfo ) => OnLogit?.Invoke( receiptInfo.Content );

// INSERTED
var completionInfo = new CompletionInfo();
zvtClient.CompletionStartReceived += ( statusInformation ) => completionInfo.State = CompletionInfoState.Successful; 
zvtClient.CompletionDecisionRequested += () => completionInfo;
// LAST LINE INSERTED



var res = await zvtClient.PaymentAsync( sum );