@s.semashka I still think that it’s because it’s not finding the credentials file.
Here is the code that creates the path to the credentials file:
static string assemblyPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
static string credentialsPath = Path.Combine(assemblyPath, @"…\extra\credentials.json");
It gets the path relative to the currently executing assembly (aka current version of Dynamo that is running). It goes back up one folder from the DLL and then back into the “extra” folder.
What version of Revit are you running this in?