I see two possibilities.
One, you are using current VI's path constant, but in an EXE the path of a VI is different than it is in the development environment. The name of the executable file becomes a layer in the path. You may need to do a strip path when this VI is within an EXE.
Two, perhaps the file you are trying to open wasn't included in the EXE, or installed into the directory where you think it should be. Perhaps you should be using Application Directory constant.