Files uploaded but left in temporary folder without media being created

I'm getting the same error :/

I faced the same issue in 3.0.2 and was able to resolve the same by using https://unpkg.com/dropzone@5/dist/min/dropzone.min.js and https://unpkg.com/dropzone@5/dist/min/dropzone.min.css and placing them in libraries folder at libraries/dropzone/dist/min as new files dropzone.min.js and dropzone.min.css

Use this for an automatic installation.

Add a custom package to the root composer.json file. Its repositories key looks like the following.

"repositories": [
{
"type": "composer",
"url": "https://packages.drupal.org/8"
},
{
"type": "package",
"package": {
"name": "enyo/dropzone",
"version": "5.7.1",
"type": "drupal-library",
"dist": {
"url": "https://github.com/enyo/dropzone/archive/v5.7.1.zip",
"type": "zip"
}
}
}
]
Run composer require drupal/dropzonejs enyo/dropzone, the DropzoneJS library will be installed to the libraries folder automatically as well.