Plugins won’t automatically install any more

I have been adding and removing plugins on my blog and all of a sudden I stopped being able to see plugins that I manually upload.

I have been working with WordPress for many years, so I know what I’m doing (generally ?? ) … So I have checked the following

The plugin directory is 755
I’m definitely uploading them to the right directory.

The plugins don’t display in the installed directory or editor

I am able to install them manually through the installer, this is just tedious though.

This problem has been listed before, but no resolution was found.

Does anyone have a fix for this?

Thanks
Joolez