If you are unable to access your timeline even though the date is set in the future and it appears greyed out, it could be due to one of these things:
You don't have enough timeline credits left. You can create a timeline, but if you don't have any credits to apply, the timeline will become inaccessible.
Your subscription has ended. Once you cancel a subscription, we give a short grace period to export your timelines; however, after the grace period, the timelines will become inaccessible and greyed out.
In order to gain access to your timelines again, you will need to purchase timeline credit or apply an existing credit to the timeline.