Yahoo Eroor
Failed to authenticate with Yahoo!, please try again later
MacBook Air 13″, macOS 10.15
Like Apple requires an Application Specific Password when using a Third Party e-mail Client ( application ) to access iCloud Mail
Perhaps Yahoo also requires an Application Specific Password generated from Within the e-mail account you access from your Browser
Sign in to apps with your Apple ID using app-specific passwords
In which case, the previous suggestion from @John Galt would be your best bet to possibly resolve this computer issue
