What is a Tamron 600mm? Do you mean the Tamron 150-600mm? version 1 or 2?
Adobe applies the profile for The Tamron 150-600mm A011 (version 1) starting with LR 5.3 (for Canon), 5.5 for Nikon. If your version of light room is older, it won't support this change. You would need to either upgrade or use the DNG converter which I understand would have the lens correction incorporated.
In my experience with CS6 (not light room), sometimes the program has trouble auto-recognizing the lens. You might have to manually help select it (if it shows up on the list).
Yeah, I don't recognize that lens, either. You might try going into the camera menus and disabling lens correction, and AFMA adjustments.
It is my understanding that the camera identifies the lens, and adds that to the EXIF data when correction is enabled.
I figured it out on my own, Initally I imported photo from Photos on my Mac to Lightroom, If I import directly from camera to Lightroom it recognize's Tamron lens. for 1/2 hour talking to Adobe, i could not understand the english being spoken and had to ask repeatly to say again also there would be minutes of silence and when I would say hello Adobe rep said he was reading my case which would last for 5 minutes at a time. I will never call again.