You've probably tried this already, but in the spirit of trying to be helpful:
Have you made sure to hit the "SAT" button at the top before doing anything? When first setting up my DST-3000, I had hit one of the other buttons, which put it in another mode and the unit wouldn't respond to the remote. Again, I'm not trying to offend here, just a shot in the dark.
Otherwise, I have no clue what it would be. I wouldn't think they would change remote codes even between different models (almost all RCA models use the same codes), much less in different versions of the same model.
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