When starting the Cuba Studio 6.4 the server window appears but stays empty. See attached screenshot.
From knowing where the start button appeared in previous versions, I was able to start the server by clicking at the upper right corner. After a little while the server is running and I can access the studio on my local machine through the browser. Everything works ok.
It is however very annoying to have a blank/empty server window.
I already restarted and reinstalled Studio 6.4 but without improvement.