GTK3 theme engine

In the appearance tab in system settings, under GTK styles and fonts, under the GTK3, it claims the theme engine isn't installed. I know I installed it. I would like to get Synaptic to use the right theme because it does look ugly. This has happened on two machines, the one we use for a projector and the laptop I'm currently on. Any suggestions to try? -- Bro. Michael Henry Associate Pastor Monticello Christian Church 1 Timothy 1:15 "This is a faithful saying, and worthy of all acceptation, that Messiah Yeshua came into the world to save sinners; of whom I am chief."