Fast Archiving Enabled and Status remains "Build Pending"

Hi,

After my EV11.0.1 upgrade I have enabled a single test mailbox for Fast Browsing (Check the box on the Advanced tab of the user properties) but 48 hours laster the status remains Build Pending. I have re-provisioned, re-synchronised and archived some content and the status hasn't changed from Build Pending.

It's not a particularly large archive, is there anything I can do force/hurry the process? Is it waiting for something else to happen before it completes?

Thanks