Yahoo has been used worldwide because of its features & provides free email services. But, if you are facing the problem of Yahoo Mail Error 14 showing on your Yahoo Mail Account, then you can follow these basic troubleshooting steps:
1) Try to logout from your Yahoo Account & then sign in again
2) Check if Yahoo Mail Server is Down or not with the help of third party web applications
3) Reboot your Device & then try to use the Yahoo Mail