Perhaps, there is permission issue so the customizer cannot create css file. Please check file on your server located wordpress_installation/wp-content/uploads/jnews/jnews-dynamic-styles.css
*Notes: wordpress_installation = your WordPress installation path
If folder jnews and file jnews-dynamic-styles.css not exist, create it manually and give permission 777.
Then, back to your WordPress administration panel and try to customize and save the option again.