Nest box question

[Deborah Carstensen]

I have a nest box in my backyard on a pine tree. It has been used by wrens for several years but this year they came and left very quickly and never used the box. I noticed chickadees making a nest in the box and then they left with nest intact, no eggs.
Now I have noticed the nest box being stuffed fairly full (but not completely)with moss and feathers. I don’t know where they got the moss, I haven’t seen any on the trees. Maybe from garden containers?
I know that wrens fill boxes but I normally have seen them do that with sticks. I haven’t seen bird activity around the box but birds can be pretty sneaky! I knocked on the box and opened it slightly but didn’t feel for eggs because it was hard to reach in.
Any ideas? I’ve included a picture.
Thanks, Deb Carstensen, Arapahoe county