Screenly logo at startup but then black green

I installed the most recent version of Screenly (10.1) on a Raspberry Pi 3. It starts well and shows the Screenly logo, but afterwards I get a black screen although assets are ready to be published. Any idea what might me wrong?

Here is also the log I get. That might help to make a suggestion:

I would suggest that you re-run the installer (bash <(curl -sL and try the latest developer version.