There are two main reasons why an app that has been updated does not appear under "Recently Updated Apps" on the Google Play Store:
A bug in the Play Store. This is the most common cause. The Play Store has a number of bugs that can cause apps to not display properly.
Sometimes an app that has just been updated may even still be listed on the available updates page. When the user chooses to update the app, the store realizes that an update doesn't actually exist and the app quickly disappears.
The second is Play Store only shows apps that have been updated with a certain amount of new data or features. If an update is very small, for example if it contains only bug fixes, it may not appear under "Recently updated apps".
Here are some things you can try if an app you've updated doesn't appear under "Recently Updated Apps":
Make sure you have the latest version of the Play Store. Google regularly releases updates for the Play Store that may contain bug fixes.
Restart your phone This can sometimes solve Play Store issues.
If you've tried all these things and the app still doesn't appear under "Recently Updated Apps", you can contact Google Support for help.