Looking for Marketing Inspiration

I wish I could find something, anything, that would work for me, but my latest book is just not selling.

I've had five books commercially published (two last year) and one of them is shortlisted for a national Best Sci-fi Novel award in April. I've won other writing contests and prizes, and sold over 20 short stories to magazines and anthologies, so I suppose I'm not a terrible writer.

I have decent followings on Twitter, Facebook and LinkedIn, I have a presence on Goodreads and Google+, I also have a blog which attracts maybe 600 unique visits per month, but none of it seems to make any difference at all.

On 3 Jan this year, I self-published a new novel and have sold almost no copies. I had a giveaway on Amazon in February and hardly anybody even wanted the book for free!

In three months, the book has attracted two reviews!

I really don't know where to go from here. Does anyone have any suggestions?