Arlathan Forest Shadowy Grove Puzzle Not Completing

I hadn't done the conversation quest, so I tried doing the puzzle again after that. Unfortunately, it still didn't work. 

Maybe it's because in my save I had already read the letter prior to the conversation quest. To get back to a save before I read the letter would require me to redo hours of content. 

I'm happy this fix worked for you though and fingers crossed it helps others.