Unable to connect SMTP server

Unable to connect SMTP server

I have linked my my Yahoo mail to my Zoho account. I never had any issues with SMTP until recently. Now when logged in to Zoho and trying to send Yahoo mail, I frequently get the following error:

“Unable to connect SMTP server:plus.smtp.mail.yahoo.com Reason: Authenication failed: 535 5.7.0 (#MBR1213) Please verify your account by going to https://login.yahoo.com”

Sometimes going to https://login.yahoo.com clears the issue, but the last month or so it rarely clears the issue. Sometimes just waiting a day or two works.

I have revalidated SMTP settings within Zoho settings.

My original settings were as follows:
plus.smtp.mail.yahoo.com
port 465
TLS

I have also validated (within Zoho)

smtp.mail.yahoo.com
port 465
TLS

And Yahoo setting "Allow apps that use less secure sign in" is on

Attached is a screen shot of my error.

I have recently tried various combinations since including smtp.mail.yahoo.com, port 587, and SSL. No luck with any setting. How can I get Yahoo SMTP working reliably again from my Zoho account?