Cubik Serial Key is invalid. It doesn't let me to move to another PC. [Solved]

[MyoHtet]

I have never used cubik studio. I bought CubikStudo this morning. I've two PC.
I used my email and serial key in one PC. And Cubik was so lag on that computer and then, I try to use keys in better one. But it doesn't work. It says "Error 418. The license information can't be validated."
Then, what I got to do? I really want to use Cubik Studio. Please help me.

Note: I didn't share my serial key to anyone.

Edit: I wanna use cubik studio in another PC. then, tell me how to logout from old PC.