What is wrong with the header? I am checking and it works well. Do you mean it is transparent in the beginning? You can set the color in the row settings https://gyazo.com/47f5c891f28b9849854ad9dff9483ad1
If it is not what you mean, please provide more details and screens of the problem.
Thanks for your reply. My problem is on demo when I scroll down and again scroll up to the top, header expands.
But in my site scrolling down and up header not behaving like in demo.