GeneratePress compatibility

Hi, I’ve just bought your plugin, because its awesome and simple. Thanks a lot. BUT ?? I’ve a problem. I’m using GeneratePress theme (bought it too, so changing to another one is the last option) and with sticky header, the background (color) disappears, when I scroll down a bit and return to the top of the site. Can you help me with that? Thanks in advance.

The page I need help with: [log in to see the link]