Just because he doesn't put his tail up doesn't mean he's not happy. My two, Book and Neelix do always have their tail up but my MowMow (died in January at 16 years old) NEVER put his tail up. He purred, loved on me, was a wonderfully content cat. He just wasn't one for sticking his tail in the air.
My newest addition Jack Jack never puts his tail up either. He's a happy boy who purrs and plays and loves to cuddle, he's just not for sticking his tail up.