Field type files not working

I want to add a file upload to my panel.
For this purpose I chose type: files like so:

                label: image
                type: files

The field appears in my panel, but if I press “add” and than “upload” nothing happens.
I would have expected a file browser opened.

No js errors are reported in the console.

Would be great if someone can tell me what I have done wrong.

Kirby version 3.5

If you just want a place to upload files, then a files section rather than a files field would be the better option. A files field is intended for you to select files out of a set of files.