Hmmmm. You've collected every time piece, right?

I’ve collected all of the ones in the base game. I still have the rumbi factory, as well as the second and third acts of the arctic cruise.

I think with the DLC, you need to get the DLC time pieces as well before it becomes available.

You’ll need every single time piece BEFORE the tour rift in order to access it. The time rift should be located next to telescope in the attic once you’ve gotten all the others.