Overnight, my iPhone throws up an error message stating username or password is incorrect. Theres a link to 'settings' in the message which takes me to the account settings and a message which says 're-enter password'. Re-entering the password has no effect. Emails up to last night are viewable but their are no emails from today.
It worked fine last night and i haven't changed anything. i updated the phone to the latest IOS several days ago, so its not that.
Better, i have 5 BTYahoo email accounts on my phone and the others all work fine, just the one account ( call it 'ABC' account) throws up the error.
Better yet, i have the exact same accounts on my iPad and they ALL work fine on that device, including the ABC account.
However, my wifes iPad has thrown up the same error on the same ABC account. after
BUT, HER iPhone, which has never had the ABC account on it, has just accepted the new set up of this account and downloaded all the emails, up to date.
I dug out my 'old' iphone, not used since before christmas, selected the ABC account and all the last months worth of emails updated OK.
I deleted the ABC account from my wifes iPad, power cycled it and tried to set-up the ABC account but it wont accept the credentials, just bounces back to the setup start screen ('select your email service' screen).
Finally, going back to where i 're-entered password' on the settings screen, whilst it had no resunlt on the phone/iPad itself, each attempt did generate a new email into the ABC account mailbox (veiwable on the other devices) from Yahoo titled 'New sign-in on iPhone' or iPad as appropriate. i have 9 such emails so far!
Have you tried the obvious thing by switch the phone off and back on again?
If that doesn't work, because you have not changed anything and your account is still accessible on the other devices I would suggest that you leave things alone over a day or so to see if it sorts itself out. Changing settings and resetting up accounts and changing passwords that are obviously working may cause more problems.