Okay, here is some very basic help …
a) review your “page source” to see WHAT your meta data “actually” looks like — ignoring anything in the Yoast admin pages.
Does the META data in your post page head look correct; is the correct description there?
b) if no, then you may have issue with plugin conflict, site setup, theme issue and you will need to debug which element causing plugin to NOT work
bb) if yes, then you have to wait for Google to re-read your pages and see the new elements and update their dbase.
c) you can force this a little bit by resubmitting your sitemap via your search console account (webmaster tools)
Obviously remember when you change your meta data a good common practice is
1) clear caching plugin and/or CDN caching
2) potentially clear mod_pagespeed cache if using it
3) clear transients with wp-optimize plugin or similar
4) resave permalinks
5) change the Yoast sitemap size from 1000 to 999 which makes different set of indexes; then ‘test’ and ‘resubmit’ via search console; worst case delete old sitemap in your account and resubmit as new sitemap.
All of those may help some of you new to this whole process.
On the other hand, note there are some wonky things with the plugin I have reported as a PRO user + news seo add-on. So, your mileage may vary ??