Custom CSS not saving in live preview

I’m using the customizer to apply the custom CSS for the buttons in my site. The changes appear in customizer view but when I save and go to the live preview, it doesn’t apply. I also noticed that the custom css file in the live preview page doesn’t apply the changes I made in the customizer.

This is the preview of the page in customizer: http://prntscr.com/SUXKNkfegUmf

In live preview, it still shows as this: http://prntscr.com/2onUxJzjfE0b

I already tried to clear wordpress and browser cache and regenerate CSS. I also tried private browser but nothing worked.

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