can't access Comcast email from Apple Mail Client on iPhone and Mac

I have a primary and multiple other email addresses under my account, one of which is my wife's email address. I am a current customer and I use an iPhone, iPad and Mac to access my mail accounts  Per security requirements, I recently updated my email address passwords (except my wife's user account) by logging in via the web browser . 

Prior to updating passwords at least 4 of my email addresses were receiving/sending mail just fine, using the Apple mail client on my Mac and iPhones. Afterword, those all stopped working with Apple mail client on the Mac and iPhone. My OS and iOS are up to date. I have checked the 3rd party email setting in each of these comcast email addresses (signed in via browser) and it is enabled.  I deleted several of the email addresses on my Mac accounts/Mail settings and tried to reconnect to them, but couldn't add these email addresses back.  My iPhone and Mac Mail cannot access Comcast email, are broke and offline, for a couple of days.

So far, we haven't disturbed anything on my wife's email address - no password update or anything.  She uses a PC with MS Outlook as her client and Apple mail client on her iPhone.  Her email seems to continue to function.  I'm leaving it alone.  I'm not ready to descend into "Tech Support Hell" trying to get her stuff to work, when I can't even understand how to get my own, normally well-behaved stuff to work.  

I can access and manage all the email accounts via web browser.  For the email address names I personally use, I've changed passwords multiple times (on the web) to ensure I was using the correct passwords in the Mail clients. Thinking it might be a Xfinity/Apple Mail client interaction problem, I've installed several other Mac mail clients (Spark, AirMail, Newton) to see if I could get around the problem.  No Luck.  I can't get Spark to connect to my email on Xfinity servers and I'm holding off on the other clients.

It's not long term sustainable to continue with web only access, especially since I can only access one email address at a time via browser.  There are multiple web sites, companies, IRS, banking, medical and other things that are all tied to a specific one of my multiple Comcast email addresses.

I'm usually tech savvy.  I've been an engineer since the late 1970s and one of the early adopter and a leading hands-on computer users and network administrators in the 1980s-2000s, in a medium-large corporation. I continued to be a major computer user and did specialized non-commercial software development thru 2019.  I say all that to say, I can usually understand technical problems and troubleshoot them.  I am totally flummoxed and frustrated here. Xfinity, Apple and their interface issues are all a black box. I could really use some Xfinity tech support help.