Entrance Small Soul core mechanism

After entering Jiquani's Machinarium for the first time I went and summoned Alva. I then fought the monsters in the area and dropped the small soul core.
With the soul core in my inventory i clicked the stone altar and nothing happened. I also tried both right and left clicking the core in my inventory and then the stone altar. So i cannot proceed

I was having the same issue.

Opening a new instance of the area fixed th issue for me.

[you can opena new instnance when traveling to the area by holding Ctrl on your keyboard when you click on the waypoint on the map and selecting "New" from the pop-up window]