Meltnatty Said:
"Deleted a yahoo email account and can't add it back: I deleted my bellsouth.net (yahoo) email account from my mac. It won't let me add it back now. I get to a screen to put in my username and I do and then when I hit "continue" it does nothing. It won't go forward and it isn't thinking."
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Use a New App Password for Each Device:
Do you use an App Password? If so, try a new App Password. Create a unique one for each device. Remove the current one, and then use the new one instead. Sometimes, changes (i.e. updates) are made to the device, and then mail server syncing becomes an issue (which is what a new App Password it intended to fix).
Yahoo App Password Link: Generate and manage third-party app passwords | Account Help | Yahoo