I can’t get this to work either, although I’m not having the upload issues.
I activated the plugin, filled in all the settings, selected the file (png), and tried to manually add the watermark to a few files. They are not showing up.
I had tried using Watermark WP Image Protect with no luck, and it’s not suppose to permanently alter my files, but that old watermark is still showing up in a few pictures. I deactivated and deleted that plugin and it made no difference.
Please help!