E-mail from a specific address is being blocked by Comcast

All incoming e-mail from the address technicalsupport@welchallynhome.com has been blocked by Comcast since 5/9/2023. No problems before that date. It may affect all addresses in that domain. The company, Welch Allyn, advises that there are reports from other users of the same issue, with different ISPs. I created a new login with a Gmail account and the mail was sent to the spam folder and I was able to whitelist it successfully. But with the Comcast account it's not even making it to the spam folder. How do I get this whitelisted or unblocked?