I have recently installed OJS 188.8.131.52 in a subdomain (i.e: ojs.mydomain.com).
Now, tried to install a plugin (theme: [Manuscript (Default child theme)]) from plugin gallery, but it gives a error/notification message like:
The uploaded plugin archive does not contain a folder that corresponds to the plugin name.
Instead i have manually put a zip file to cpanel on the folder: ojs.mydomain.com/plugins/themes, named CLASSIC THEME
Extract that and give 755 permission to the whole folder.
After that, i have also get that theme to the installed plugin list, from there i checked the box to enable it.
But, still in the APPEARANCE > THEME dropdown list, this classic theme is not shown, only the default theme is shown.
However, i have again put an external CSS APPEARANCE > ADVANCED option, but also no reflection of that as well.