[Bug] Ritual Alter can't be activated

I'm in a Maze map, 0 monsters remaining, but I'm unable to click and activate my last ritual alter.

It's the one that summons the fire dude who casts AoE fire circles at you. The altar spawned in a relatively thin passageway in the map, so I'm wondering if that has something to do with it?

Either way, I assume not intended.