Well, there are two things that could be the problem. First, when exporting, does a sign come up saying that something's missing? If so, check your libraries and make sure you have all the files in the right place, and that nothing is missing. Second, ask your friends if they can see the object, but if it's black and yellow, then a material file is missing. If it comes out pure white, then the object itself is missing. Both can be fixed by making sure the object file is in the right place and making sure it's not missing. Hope it helped. I'm sure others could give you a more detailed explaination.
