As already said, VI references (like other references) are only valid in the application instance they were created in. If you want to get a VI reference in another instance (another project or target or EXE) you need to enable VI Server access on that instance (read the help on how to do this), then use Open Application Reference with the correct IP address and port number configured for that instance and then Open VI Reference with the correct VI name (assuming that VI is already loaded in that instance) and that will give you a reference to the VI.
Also, note that access from an external process is limited and you don't have permission to call all the properties and methods. Each property should have this documented in its help page (under "remote access allowed").
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