Installing wp defender plugin, fails every time

Hi everyone,

When I try to install wp defender, I always get a failed install warning. Every time it tells me that there might be wrong permission settings on wp-content folder but the permissions are OK! as they are set to 755 on wp-content (as this tread here suggests https://premium.wpmudev.org/blog/understanding-file-permissions/) which I have changed with ftp filezilla.