Yahoo mail settings error accessed by Mint?

On a Mint 19 desktop my mother has Yahoo mail. Her friend borrowed use of her computer, now Yahoo mail doesn't work properly for her. Her email list is shortened to about ten new emails. Options she normally uses as faint and when clicked on, they don't respond. Is there a way to alter Yahoo setting back to normal?The settings button itself doesn't respond, but it seems mostly fine in Firefox. She usually uses Chromium.
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