WCF LOB Adapter Exception "Melden Sie sich mit einem Dialogbenutzer an"

If you receive the folgenden error message in the SAP WCF dialog:

Connecting to the LOB system has failed.

Details: ErrorCode=RFC_OK. ErrorGroup=RFC_ERROR_LOGON_FAILURE. SapErrorMessage=Melden Sie sich mit einem Dialogbenutzer an.  AdapterErrorMessage=..

...you might have set AbapDebug to "true", like I did in my WCF URI "sap://CLIENT=800;LANG=DE;@A/sap.host.de/00?ListenerDest=ABC&ListenerProgramId=DEF&RfcSdkTrace=False&AbapDebug=True"

If you set AbapDebug to "true", you have to log on with a Dialog user.

WCF LOB Adapter Exception: "Connect from SAP gateway to RFC server failed"

If the WCF LOB Adapter Pack receives a RFC_ERROR_COMMUNICATION from SAP saying "Connect from SAP gateway to RFC server failed", you have to double check that all network settings are correct so that send and receive are possible. In our case that NATting of the response did not reach us, while we could track our call successfully on the firewall.
Other reasons might be SAP configuration or missing entries in services file.