Nuendo 5.5 activation code issue resolved

I’ve used Nuendo5.5 trial version for about 1 month after that i brought a legal copy of Nuendo 5 at my local dealer.
Now i want to updated to Nuendo 5.5 and it doesn’t let do that.
I’ve already tried to install Nuendo 5.5 again and it appears as Nuendo 5.5 trial version
What am i doing wrong?

thanks a lot