SAP SNC connection from outside the customer environment

Hello all,

we are trying to connect a SAP R/4 system via SNC to a oneIM 8.14. Unfortunately, the OnIM is located completely separately outside the customer environment. The connection without SNC works!

SAPcryptolib is located in "c:\sapcryptolib".
$SECUDIR is set "c:\sapcryptolib\sec".
PSE file is in c:\sapcryptolib\sec
cred_v2 file creates me sapgenpse for the system, the logged in user and the user running the JobServer service.

We go through a MessageServer.

SNC host name is configured as in SAP system,
SNC Name is the SNC name which is in the certificate.

SSO is not possible, therefore username and password.

sapnco.dll Version
sapnco_utils Version
sapcrypto.dll Version

Error: [VI.Projector.Connector.Base.ConnectionTSBBrokenException] System not connected

The tracelog of the SyncEditor is not very helpful. Also does not show more.

What I wonder:

1. how does the SyncEditor know which PSE file to load.
2. can I still create a RFC trace?

Has anyone done such a connection before and can help me?