Problems uploading free Graph Paper Press themes

I’ve been trying to upload a couple of the free themes available from Graph Paper Press (namely Gridline and Berlin). Once I’ve uploaded theme through my ftp, they appear in the themes section but do not display a thumbnail of the theme and when I preview it looks as though css is not being applied. I really have no idea what’s going on as other themes I upload in the same way work fine and I’ve tried deactivating all the plugins but that doesn’t make a difference…

Unless you become a paying subscriber you can’t access the Graph Paper Press forums, so I’m hoping someone here can help out?

Many Thanks,
Nicole