Comcast email and Apple Mail not playing nice

Comcast.net email address for decades.  Added internet account to new MacBook Air running Sequoia and apple mail client.  Working fine.  Trip to Asia.  Unable to send from comcast account, but still receiving.  Then a few days later unable to send or receive. Webmail works fine.  iOS (iPhone and iPad) works fine.  Return to US.  Problem persists on MBA, but iOS and my old desktop Mac still able to send and receive.  I delete the account form the MBA and try to reinstall it.  Now it won't accept the reinstall ("account or password" cannot be verified).  2 hours on Xfinity phone support going around in circles.  not sure it was a human.  Next step?