iPhone mail
I am not receiving email from only one of my contacts. I’ve made sure the email address is correct and not blocked. I was receiving mail from this contact, but it stopped three months ago.
iPhone 13
Check setting on your mail server and make sure there is no rule to filter that mail. Other than that, have them verify that they are able to send mail to others. Check to see if they have another email account and try to contact you with that. Check your Junk Mail folder and see if they mail is going there.