Either your host hasn't enable the zip or gzip module (Cant rememebr what it is called) or it is something else I cant think of. Oxwall dev will be able to put the finger on this tomorrow.
I installed the pluggin (s) manually and when I look in the admin ...language ... the pluggin installed is not in the list.
But I'm still not the answer to my error message : admin + manage_plugin_add_extract_error