Loading images using FirebaseUI and storage references

I am trying to load images into a collection view using FirebaseUI following this pattern. For some reason, the default images are loaded, but then the images I'm referencing in the Google Storage never appear. When I look at the references, they all appear to be correct, but the images still won't load into the image views. Here is my View Controller:

class EventViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {

    @IBOutlet weak var postColView: UICollectionView!

    var posts: [Post] = []
    var event: Event!
    var ref = FIRDatabase.database().reference(withPath: "post-items")

    override func viewWillAppear(_ animated: Bool) {

        ref.queryOrderedByKey().observe(.value, with: { snapshot in

            var newItems: [Post] = []

            for item in snapshot.children {

                let newPost = Post(snapshot: item as! FIRDataSnapshot)

                newItems.append(newPost)
            }

            self.posts = newItems
            self.postColView.reloadData()
       })
    func collectionView(_ collectionView: UICollectionView, 
        cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! PostCell

        let imageView = cell.postImageView

        let picRef = FIRStorage.storage().reference().child("\(posts[indexPath.row].imagePath!).jpg")


        print(picRef)
        imageView?.sd_setImage(with: picRef, placeholderImage: UIImage(named: "IMG_2684"))

        return cell

    }
}

My guess is it has something to do with the default images being loaded, but then the views not being refreshed once the new image is downloaded.