Fullscreen does not work anymore

I like Shrook and used it since Apple stripped Mail of the RSS-Reader. I updated to the latest version of shrook today via the App Store and for some reason the fullscreen toggle on the upper right side of the window disappeared. I found no way to get it to fullscreen mode. If anyone can comment or help me out I whould give Shrook 5 stars right away. Thanks.

comblair about Shrook RSS Reader, v2.86