How do I reach the Arch-Mage? [duplicate]

I started the "Under Saarthal" quest a while ago but stopped because I couldn't find the Arch-Mage as the final part of that quest.

Now I'm working on it again but no matter how many times I leave and come back, wait, load previous save files, or wonder aimlessly around the college, the Arch-Mage will not come down from the upstairs door in his quarters. And a key is required to open that door but for me to obtain it, I will receive it after he dies.

I've looked at so many others' similar questions but am not finding an answer. I've gone back to Saarthal and spoke with Tolfdir. A lot of people were saying that he's either in the courtyard or sitting in a chair in his room, which he isn't. At first I didn't realize it was to that top door because when I have the quest selected, it sends me out of the college and behind it between the college and sky temple ruins. I can't access the area where he is by going through the hall of attainment. I've tried going elsewhere and waiting and sleeping and returning but nothing changes. He doesn't go to bed, he doesn't come out at all. I'm thinking I must have missed something. Someone else wrote that I had to get the scroll first from alftand, I've had that before I reached this problem.