At one point during the Plight of the Rebels quest chain in Assassin's Creed: Origins, you will find yourself in a room below Alexander's Temple. During the quest the boy you saved will ask you to find another way out of the room since he is afraid to go out in the water. It is fairly obvious where the game wants you to exit, since there is a large bookcase that blocks the exit, only blocked by a few breakable vases.
The problem is that a lot of players are unable to open the passage that is blocked by the bookcase, and when trying to move it, nothing really happens. This is a well-known problem, but it's easy to fix.
What you need to do is first to move the bookcase a few steps back. It's not perfectly aligned with the track that you need to use to move it asides, but it will be if you fully drag if back first. Once you drag it a bit back, you should be able to move it on the tracks and open the exit out of Alexander's Temple.