If the sign-in failed:
- verify the mailbox name has been entered correctly;
- verify the password has been entered in the correct language and that Caps Lock is off.
If you forgot you password, tap “recover my password”.
Please note that due to a recent change in Yahoo security settings there might be problems with @yahoo.com accounts. If you use such a mailbox and encountered difficulties adding is to the application, or sending and receiving messages in it, go to «Account security» settings and switch “Allow apps that use less secure sign in” into the ON position.