Back to level 7 Chamber of Sins level 2

I missed the Trial of Ascendency the first time I went through the Chamber of Sins on act 7.
Now I am on act 8 and found that out.
I tried to go back but I cannot go down the stairs from level 1 to level 2. The stairs are not working.
Is there another way to get back to level 2?
Is this a bug, that once you complete the quest you cannot get back to level 2?
Thank you.

No there is no bug, you can go back to any area in game at anytime, no matter your level.
Try resetting the zone.