Problems connecting to AT&T Yahoo email on my iPhone after upgrade to 13.5 and iPad to

I upgraded to 13.5 on my iPhone X and 12.4.7 on my iPad Air, after which I started getting errors when trying to get ATT Yahoo email. I still receive mail from my Google account, but my ATT Yahoo account will not connect. I've tried deleting the account on my iPad and re-adding it with no success. When I go in and try to add the account service, it briefly opens a web page on imap.mail.att.net and then closes. My account is still working on my iMAC so I know my userid and password are correct.

I have not deleted the account on my iPhone, but am still not able to authenticate on it to ATT Yahoo either. Same issue, opens the web page and then closes.