There seems to be an issue with updating the LayerSlider plugin, as I am having the same problem as many other people on the forum. I have been trying to update LayerSlider all day, but have been unable to do so.
I deactivated and deleted my older version of the plugin, i.e., version 6.5.1, then tried to reinstall the new version via Appearance > “Install Plugins”. This didn’t work.
Then, I downloaded the plugin from http://hb-themes.com/repository/plugins/layerslider.zip and installed it, but version 6.5.1 installed.
Perhaps the updated plugin has a different url, because it seems this particular url is pulling the older version of the plugin.