Hi, congratulations on your new tablet and welcome to the forum. I'm moving your thread to the Samsung Galaxy Tab 8.9 section for you, where more people are likely to join the discussion and try to help you solve that rotation problem. Good luck!
Hi, I'm not familier with your tablet, but check arount the edges for a small switch. Some tablets have a screen lock switch on them that prevents auto rotate.
My Toshiba thrive would rotate when I first got it and then it stopped. I was puzzled and miffed at the same time. A member here told me to look for it and see if i had accidently moved the switch to lock and I had. Moved it back to rotate and it has been good since.