Thanks again for your message!
Unfortunately it did not work. I double checked I am in "category" not "categories". I also reset Options, Categories and Downloads Permissions in the "Tools" panel, without success neither.
What can I do to help solving this issue? This is a fresh install of JDownloads, it is ok if I remove it to reinstall, or change all the needed options.
There was also another problem in multilingual setup that was not related to the above errorColin