sorry I think I'm still missing the point - my private sense impression of a computer may be different to your private sense impression of a computer, so long as we both agree to call this thing we experience a computer, surely we can communicate practically? how can this refute representative realism?
Wittgenstein's answer to your question is that we can communicate successfully exactly because
it does not matter whether your private sensation of the computer is different from mine (if it is) because since when I we use the term "computer" neither one of us is referring to his private sensation of the computer (if there is such a private sensation) but rather we both are using the publicly shared meaning of the term "computer". In fact, that is why in his discussion of the "beetle" Wittgenstein holds that it does not even matter whether there is a beetle in the box each one of us has. Since neither one of us is referring to his private beetle. For if we did, we could not communicate. I think you miss Wittgenstein's argument which is a reductio ad absurdum
argument of the position that terms like "pain" refer to private sensations, much less that terms like, "computer" refer to private sensations. For the argument is that if those terms did refer to private sensations, then we could not communicate. But since we can communicate, they do not refer to private sensations. You seem to be arguing that since our terms refer to private sensations, it must be possible to communicate if they do. But that is exactly wrong. Wittgenstein's argument (as I said) is that since we do communicate, and we could not communicate if terms referred to private sensations, it follow that terms do not refer to private sensations. That, in other words, there can be no private language, since if there were, we could not communicate using it. Do you see the difference between your position and Wittgenstein's?
As for Representative Realism, that view argues that our private sensations represent (or resemble) public objects (your example of your private sensation of the computer and the public computer). But Wittgenstein holds that if there were such a thing as our private sensation of the computer such a thing would be useless, since we could not communicate if such a private sensation were the meaning of (say) "computer". Like the beetle in the box, the computer in my head (rather than the computer my desk) "drops out" There are not two computers: one the private one in my head, and the other, the public one on my desk. And the view that there are these two computers (not just the one on my desk) underlies representative realism.