Cache not created on my site

I only have WP, Standard theme and fastest cache active on my wordpress, but the cache is not created – so i do not see the “<!– WP Fastest Cache file was created in 0.330816984177 seconds, on 08-01-14 9:01:35 –>” at the bottom of my page.

Also the Folders in wp-content are empty and writable. What can i do here? Or how can this be debugged?

Best, Tom

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