The ready images on our website have the drivers for the non-HDMI LCD that connects on the GPIO and disable HDMI port. This is the reason you see nothing. I assume everything else is working all this time for you but the screen.
Documentation: Click “Documentation” on our website’s main menu 
Or read through the driver installation steps below and undo the HDMI disabling:
wget http://www.hestiapi.com/download/LCD-show-170703.tar.gz;
tar xvf LCD-show-170703.tar.gz;
cd LCD-show/;
sudo ./LCD35-show;