New accounts not working, pop up msg - password required

I had two accounts on the drop down list on free trial version that I wanted to change, so I
added two new accounts and it seemed fine. I deleted old accounts assuming they could still
receive emails. Then I got error messages for new accounts / password required and now
none of my email accounts can send or receive emails.
This is for my pc only so I set it up with POP 3, and I used suggested comcast configurations.
What can be done to fully activate new accounts and receive emails again for former accounts?

I still need assistance adding new account. Comcast walked me thru allowing 3rd party access to my email. Still getting message ---- your credentials were rejected
Password required- Error Authentication Fail
Password required Auth -less secure Auth - disable
email connecting failed temp server unavail or incorrect settings

I am using my comcast/xfinity user name/password, is this correct?
Is this a password problem? User name problem?
Am I using correct Incoming Mail Server imap.comcast.net port # 993 with SSL on
Outgoing Mail Server smtp.comcast.net port # 587 (or 143) with SSL on
Also tried POP3 pop3.comcast.net port # 995 with SSL

I was on the phone for an hour. He said I was good to go. It still didn’t work so concast said contact
eM Client. Need info from someone who has been there. I am new to this but I’ve researched this extensively. Just a little help might do the trick.