If you are facing Yahoo Mail Not Working on Android, then, first of all, make sure you are using the latest version of the browser. You can also try force-stop and restart the app as It refreshes the active memory of the application. This issue can also arise because of excessive cache and cookies. So clean the browser by clearing cache and cookies to get the issue fixed.

Also Read:-

Change Signature in Outlook 2010
Outlook Email Search Not Working
Recall Outlook Email on Mac
Create a Business Gmail Account
Change Gmail Theme On iPhone
How to Talk to a Live Person at Yahoo