If you’re having problems uploading your files, one of the common cause of being able to connect but not being able to upload is by using an FTP application called Cyberduck.
Unfortunately due to the way this particular application works, it’s not compatible with our FTP servers. Any other FTP application you choose will work fine. Filezilla is a free and common choice that our contributors report being reliable.
Unsupported file formats
Another possible reason why you may be having problems is if you’re uploading unsupported file formats.
Submitting .zip files is unfortunately not possible as .zip files can’t be read by our servers. On the other hand, folders are perfectly fine for bulk images.