Comcast.net email-->Gmail -- I can send from gmail using comcast as "from" account, but do not receive incoming email

No. With all my accounts, including this one, sending emails from within gmail using the comcast address works fine and there are no errors. 

That's what makes this problem weird--it's kind of the opposite of the typical problem.  The problem is not with sending emails via comcast accounts from gmail--that works fine for all email addresses. Instead the problem is only with one of my comcast email addresses where eceived emails being arriving in the comcast mailbox but getting stuck there and never making to the gmail mailbox.

And the problem is with only one of my comcast addresses. With my other comcast addresses accessed via gmail, everything works fine on both the sending and the receiving end.  It's just one of these addresses where sending works but receiving is stuck.

To be clear more generally, I've seen no errors at all of any type with any of my addresses, either sending or receiving.

I did completely rebuild it on the google side--several times. Unfortunately, I haven't gotten a different result.  And now we're 4 days in so it doesn't seem like waiting a few days makes any difference.

I've tried smtp.comcast.net with both port 465 using SSL and also port 587 using TLS.  Same results with both: sending works, but not receiving.  The messages (new & old) are still stuck in the comcast mail box and never make it to the google mail box. 

(And, to confirm, this same setup works for both sending and receiving for our other comcast addresses--it's only this one address where sending works but receiving doesn't.)

Let's take this to DMs so we can check on the account and provide some insight from our end. If you could please send me a DM with your first and last name along with your full-service address, we can get started.

To send a "Direct Message" to Xfinity Support:
Click "Sign In" if necessary
Click the "Direct Messaging" icon or https://comca.st/3EqVMu7
Click the "New message" (pencil and paper) icon
The "To:" line prompts you to "Type the name of a person". Instead, type "Xfinity Support" there
 - As you are typing a drop-down list appears. Select "Xfinity Support" from that list
 - An "Xfinity Support" graphic replaces the "To:" line
Type your message in the text area near the bottom of the window
Press Enter to send it
See https://comca.st/3KQF8q9 for an example.

I have followed the instruction and sent the DM with these same details.