[Plugin: WPDM] Shortcode error

Hi,

I’m building a new website and am also trying to add the WP Download Manager plugin. Somehow the shortcode for tree [wpdm_tree] doesn’t work, while the other shortcode [wpdm_all_packages] does work. I’ve read some other articles about the same error, but all those issues should be fixed with updates by now. Does anyone know how to fix this?

The purpose of adding this plugin is to recreate a dropbox-like environment. Does anybody know any other plugins which can do the same, or even better? In the case this doesn’t work out..

Thanks and sorry for my poor English.

(btw before you ask, website link is http://www.huitema.me but its password protected atm)