Hi supersuf,
Thanks for your query. The plugin uses the standard media library, so are you able to provide more details on where/when this occurs?
Have you tried uploading the image first to your Media Gallery by going to your admin panel and selecting Media > Add New, uploading, then going to Settings > Heroic Favicon Generation and selecting the just uploaded favicon.
If it’s a new install, it could be an issue with uploads generally, which are handled by WordPress itself, have you managed to upload other media successfully?
All the best,
Richard @ HeroThemes
Closing due to inactivity.
Richard @ HeroThemes