Doors to the Past achievement - Rune of the Seed

Hello,

I have been trying to obtain the last 5th rune (rune of the seed to be specific) since yesterday and it is just not dropping, I haven't unlocked the hidden achievement yet so this is my first attempt, all other 4 runes are placed already, so am wondering if any prerequisites exist because seriously I don't believe it should take this long since its a daily activity.

And I can't start over because the other slots are not resetting. Also "A Star to Guide Us" story is completed so I can't figure it out.

Thought I would check here before I contact support.

Appreciate any assistance.

Thank you