Through further investigation, we have found that the created projects are publishable manually by opening the project in TradosStudio and choosing Publish Project from the tool bar.  We used the same server definition and credentials in Studio as were used in the API, so we don't believe this is the issue.  Any thoughts on why API invocation would behave differently or where we can see more detailed indications of the failure reason would be appreciated.

Hi Chris Pulsifer, I'm wondering if this issue is related to the fact that you are working with unsigned plugin.  Currently, it's not possible to execute unsigned plugins from project automation as it poses security concerns.

Are you working with an unsigned plugin in this process?

I don't think what we are doing would be considered a plug-in, it is a full application.  We are effectively driving studio from our app.  Any plugins we are using would be from RWS/SDL.

To clarify, we may have plugins in use in Studio via our templates (possibly Google ML) but my code is a full application that is driving Studio SDK to create and publish projects 

Hi Chris Pulsifer, Nathaniel Goodyer,

I was able to reproduce the failed attempt to publish the project, with a null exception.  The full message returned from the server was: "Failed to publish the project".  This occurred when I included an additional path separator (e.g. /) at the end of the organizational path parameter.

Excluding the separator from the end of the organizational path parameter resolved the issue. 
Note: if the path is at the root, there should exist one forward slash.

Example of working solution:

var result = project.PublishProject(
new Uri("http://gs2017dev.sdl.com"),
false,
"USERNAME",
"PASSWORD",
"/Test API",
(obj, evt) =>
{
	Console.WriteLine(evt.StatusMessage + " " + evt.PercentComplete + "% complete");
});

Hi Chris Pulsifer, Nathaniel Goodyer,

I was able to reproduce the failed attempt to publish the project, with a null exception.  The full message returned from the server was: "Failed to publish the project".  This occurred when I included an additional path separator (e.g. /) at the end of the organizational path parameter.

Excluding the separator from the end of the organizational path parameter resolved the issue. 
Note: if the path is at the root, there should exist one forward slash.

Example of working solution:

var result = project.PublishProject(
new Uri("http://gs2017dev.sdl.com"),
false,
"USERNAME",
"PASSWORD",
"/Test API",
(obj, evt) =>
{
	Console.WriteLine(evt.StatusMessage + " " + evt.PercentComplete + "% complete");
});

Thanks Patrick, I'll give that a try.

We construct the organization path based on destination language or "Test" , but we do not have a trailing '/' in the argument we pass in.  Also tried hard coded "/Test" and that failed.