Cannot upload or install WordPress plugins

Hi there,

I am working on a WordPress site hosted by Parallels and uploaded via the plex panel.

When I want to install a new plugin, I first get notified that the plugin has been successfully installed – but when I click ‘Activate’, I get an error message saying

‘The plugin does not have a valid header.’

I am not sure what the problem is, and it does this for every WordPress plugin I try to install. Help!

When I try to upload the plugin manually by browsing for a folder and clicking upload, I get a different error message:

‘Unable to create directory wp-content/uploads/2013/12. Is its parent directory writable by the server?’

These two errors are really puzzling and neither myself or my client can install any plugins. Can anyone offer any help with this? Please?

Regards,

Robert

Site @ freebuildingphotos.co.uk