BT Yahoo mail users sometime start to face a problem where their mail account with BT stop working on their mobile phones, tablets, PC all at the same time. This locks them out of their own email account and leaves them feeling helpless, especially when the user is absolutely sure that the password they are entering is correct. Then, they try to delete the password, then re-enter it on their devices, which will more often than not make no difference. The next option they see is to entirely delete their account from all of the devices and then enter it again, thinking that will solve their issue.
In such a scenario, changing the password, deleting the account and then re-adding it will prove to be pointless because the problem has shown itself in more than one device. Deleting the account and then re-installing it may in fact give you further problems that will take you a long time to resolve.
This issue happens sometimes but is known to resolve itself without any problems. You should try and access your email account via webmail. Another option you have is to use the server settings for Yahoo. This has proved to be helpful to several users, where they try and access their account from a single account while keeping al other devices shut off. This way, only one device is trying to access the email account, instead of several of them trying it at once.