Getting Error in function SessionOptions()

Hi,
We have implemented WinSCP API in .Net application. It working properly but from a few days back we are getting connection failed error. After deep investigation, I found that there is an error from class SessionOptions constructer SessionOptions(). Can you please suggest why we are getting this error. Nothing is changed from our end.

Stack Trace : at WinSCP.SessionLogReader.Read(LogReadFlags flags)
at WinSCP.ElementLogReader.Read(LogReadFlags flags)
at WinSCP.SessionElementLogReader.Read(LogReadFlags flags)
at WinSCP.CustomLogReader.TryWaitForNonEmptyElement(String localName, LogReadFlags flags)
at WinSCP.CustomLogReader.WaitForGroupAndCreateLogReader()
at WinSCP.Session.Open(SessionOptions sessionOptions)

Sorry, but can you share the exception error message?
Or even better, a complete session log file?