upgrade from AX3 to AX2009: Cannot doing the postsyncronization

Hello, I’m doing the upgrading from AX3 to AX2009, and I’m doing the upgrade checklist.

I try to do the postsyncronization selecting:

Administration > Setup > System > Checklist > upgrade checklist

And in the upgrade checklist I have done all the steps until “database syncronization”, and

this step is correct but the postsyncronization step isn’t active (is disabled) and I can’t select it.

I can’t continue, does someone know why it is??

Thanks in advance and greetings.