Hi Alex,
SQLNET.AUTHENTICATION_SERVICES can be set to "none" only when SAP is using SSFS completely. If even a small part is missing then authization errors occur.
Did you perform all the required steps to adopt SSFS?
1639578 - SSFS as password storage for primary database connect
1622837 - Secure connection of AS ABAP to Oracle via SSFS
Regards,
Salome