Why does libraries-extend not change part of the styles of the module DropzoneJS?

Question

I use the DropzoneJS module. To change to change part of the styles written here: /modules/contrib/dropzonejs/css/dropzone.widget.css I use libraries-extend.

In the files of my theme particle I wrote:

particle.info.yml:

libraries-extend:
   dropzonejs/widget:
     - particle/dropzone-custom

particle.libraries.yml:

dropzone-custom:
   version: VERSION
   css:
     theme:
       css/style.css: {}

style.css:

.dropzone {
  background: #f1fbff;
  border: 2px dashed #2cb7f4;
  border-radius: 37px;
}

And then I cleaned the cache. But styles are not applied.

Where is the error? Is something missing?