Load css with @media queries doesn't work.

Hello, thanks for your very useful plugin!
I have several @media queries in my css, but no style is loaded if it is preceded by:

@media (max-width: 767px) {
.....
}

Do you have any suggestions or workaround to solve?
Thank you in advance if you can help me. 🙂
Marcella

https://ww.wp.xz.cn/plugins/specific-files-for-posts-and-pages/