If you are not seeing changes that you have applied to your website, you may need to clear your cache.
This means that your visitors will be served files from servers that are closest to them in the network. For example, a user in New York will get their files from servers nearest to New York when they visit your site, while the visitors from Europe get their files served from different servers that are closer to them. This makes your site load faster for visitors.
A more detailed guide on how to purge the cache can be accessed here. This will clear the CDN’s cache and replace the stale CSS with the most recent version.