I believe that the execution of executable might not have happened successfully. For verifying that, can you check the results of the dos command. For example,
>> [status,results] = dos('foo.exe')
I see that you are using '$path' in the dos command. Make sure that the MDCS server is installed on the Windows machine (workers running on Windows) and the executable is present in the correct location which you are referring to and the MDCS server (workers) have access to the executable.
I will be surprised if there is any other reason that could be the cause of the issue.
Also, I am curious to know how you are verifying that the executable is not launched?
Note that MDCS workers run on their designated cluster machines and might not have access to your local file system unless configured explicitly.