CSS Styles are unique in nature to Export Kit and require you to place the folder at the very TOP of your document. CSS is compiled in order – last in, last out. This means that you MUST add your custom styles at the TOP of your PSD document, otherwise the layer elements will maintain their layer effects/styles without change. This includes responsive designs, keep your CSS Styles at the very top of your layers.
When using CSS Styles, it will create the styles AT THE POINT you place it in your design. We ask users to place the folder at the “top” of their design to avoid confusion. When you place your CSS Styles inside a screen or page folder, the next screen will NOT contain the previous styles – this is NOT a mistake. What you did was target the CSS Styles to render ONLY when the target screen or page is active.