If Outlook not receiving Yahoo emails, then you have to do basic troubleshooting to know the exact cause of the issue. This is a problem that occurs on Windows system, macOS, and the online version of Outlook.
Restarting your Outlook will most of the time help you to sort out many issues. Some other applications along with Outlook may hang up or stop working altogether. The best solution is closing all the apps and restarting Outlook alone. This will help to receive the emails from Yahoo.
Just look at the Outlook status bar for Disconnected, Working Offline, or Trying to connect messages. Because of the connectivity issues, Outlook is set to work offline and hence it won’t receive your Yahoo emails.
If you are not able to see new emails in the Inbox, that doesn't mean you haven't received any emails. Sometimes those messages are forwarded to the Junk Email folder. Check the filters enabled in your email account and disable or modify them as required.
If you have configured your Yahoo Mail account in Outlook using POP, then POP access should be enabled in your Yahoo Mail account.
Sometimes creating rules, will route email from your Inbox to another email account or being deleted. Now, you fixed the Outlook not receiving Yahoo emails issue.