Get the correct download url in firebase storage

I have a folder inside my firebase storage named ‘banners’
Using javascript I have successfully uploaded it to the folder.
The problem is that the URL provided by the getDownloadURL() is giving me an error
‘Invalid HTTP method/URL pair’

The link below is the one provided by the getDownloadURL() method, which does not work.
https://firebasestorage.googleapis.com/v0/b/sample.appspot.com/o/banners/imageid123.jpg?alt=media&token=sampletoken

And this is the link that is working
https://firebasestorage.googleapis.com/v0/b/sample.appspot.com/o/banners%2Fimageid123.jpg?alt=media&token=sampletoken

I noticed that it works when there is a %2F in the link, but I don’t know how it will generate a link in that format.

I hope you can help me. Thank you

Btw, this is my code.

    // Initialize Firebase
    firebase.initializeApp(firebaseConfig);
    firebase.analytics();
    
    btn.addEventListener("click", function (e) {
      e.preventDefault()
      const storage = firebase.storage();
      const storageRef = storage.ref('/banners/');
    
    
    
      const productImages = document.getElementsByClassName("drop-zone__input");
    
      if (document.querySelector(".drop-zone__input").value !== "") {
    
        for (let i = 0; i < productImages.length; i++) {
          setImageNameAndMetadata(
            productImages[i].files[0],
            productImages[i].getAttribute("id")
          );
        }
    
        function setImageNameAndMetadata(image, imageId) {
          result = "";
          for (var i = 0; i < 5; i++) {
            result += characters.charAt(
              Math.floor(Math.random() * charactersLength)
            );
          }
          var imageName = result + image.name;
          var imageMetadata = {
            contentType: image.type,
          };
          uploadImages(image, imageName, imageMetadata, imageId);
        }
        function uploadImages(image, imageName, imageMetadata, imageId) {
          var uploadImage = storageRef.child(imageName).put(image, imageMetadata);
          uploadImage
            .then((snapshot) => snapshot.ref.getDownloadURL())
            .then((url) => {
              console.log(url);
    
              document.querySelector(`.image-box #${imageId}_url`).value = url;
            });
        }

  }