Unable to activate Ritual POE2

After clearing the map (4 mobs remain) I can't activate 3 of the 4 Ritual alters.Has happened on this map before Oasis.

I can solve your problem. It's all because of the mobs with tendrils that hide underground. They can be anywhere on the map, not even near the ritual, but after killing them, you can activate the altar. I just checked it out: I had two rituals closed and there were two mobs left on the map, I found and killed one mob and one altar opened.

I can confirm, those wormy-thingies that dive in and out of the ground were the root of my problems. I literally combed the entire map with a fine toothcomb and found the remaining two. Once killed, the remaining altars opened up. TY!!!

Having Same issue.
0 monster remain on Forge Map.

Same here, 0 monsters left.

Same issue here, happened on Hidden Grotto map with the burrowing worms. 2 altars uninteractable, occasional red swirls perpetually circling each altar. Little frustrating

More than a little frustrating. I have an Audience with the King on the table and don't have enough favours to defer it without these last two altars :(

Edit: Unlocked them. I had to detonate all the corpses of those little tendriled monsters, too. They were all dead but their corpses still kept the altars from activating until they went boom.

I can confirm detonate dead on the corpses solves this!

Same bug here, hive 0 mobs left, 3 of 4 rituals cannot be opened. // Edit this was also a map with a deli mirror which not properly activated, you see fog but have 0 progress

Also same issue couldn't do a single ritual on map, 0 monsters remaining. Additional content was breach and delirium.