I just put in place a multi-language site, with Italian and Spanish languages normally working. I'm using Joomla! 3.9 and gk_magazine Gavic Pro template, but exactly the same happens with Protostar. I have two problems:
1) clicking on an element of the tree when selected language is Italian, all is working fine but selecting Spanish, jDownload Tree returns a "404: page not found" error, which is impossible, because if I reach the same point via menu, the page is correctly there.
2) from jDownload content displayed in the mainbody section of the page, logging in with a user enabled to Create downloads, same situation: using Italian language no problem but if I select the "Add" button, it returns me the same "404: page not found" error. Could you please suggest me something to verify? Both problems seems to be related to multi-language site... Thanking you in advance
[image 1 is related to normal situation clicking on "Documenti pubblici" element of the tree it works fine, displaying the corresponding content; Second image refers to clicking under same situation but under Spanish language]