style.css not updating on Wordpress
In your theme > style.css we have to add version as below
/*! Theme Name: bestTheme, Version: 1.2*/initially style sheet will be loaded but "...style.css?ver=" will be null without version in styles sheet so changes will not effect. Changing the version number of stylesheet whenever you do a change to styles is a good practice and will have immediate effect on the production. Instead there will be no cache problem.
Even after you empty your cache it will not work because your hosting site has it to work for many days e.g. 5-10 days perhaps. I had the same problem and I contacted my hosting service and viola! They said it's about the cache settings on their servers. So you should contact your hosting so that they can update the cache settings and the one you're updating will reflect on the live site. It's not your cache it's the hosting service server's cache