Why my meta description is not updating on google

Inspect the URL in Google Search Console to make it crawled immediately. Alternate way is to get some backlink for this page or get some internal link for this page. In either case it will be crawled at the earliest opportunity.

If you've recently updated your description, Google might not have crawled the page, or updated their index with your content. It can take time for Google to process the changes you made, depending on how frequently your website is crawled.