Can't Register My Game

I'm stuck trying to register my game. I have installed using both Uniloc and Steam now and both times my product key has failed to work. I type it into the Liscense Key lookup site and it says invalid. I don't know what to do next as i have followed the instructions on all of the other sites. Any ideas???

Thanks

Is it a new game or second hand? If its second hand then maybe all the times you can install have been used up. There is a thread telling you how to get some of these licences back but cant seem to find it so contact customer services for more help or check some of the threads about authentication on this forum.

I'm using Steam version and I didn't need to actually activate it, it did everything automatically.

If the key is invalid talk to Steam to give you support, perhaps send you a different key.