Password sync to O365 not mapping email and UPN

I have setup password sync with O365 using a global administrator account (confirmed login on the O365 portal). I have password sync agent installed on DCs on the network and I see the audit report showing the password reset on local AD for an account. The account has the UPN domain matching the O365 domain, however the username is different than the email address. The email address in local AD matches the email address (UPN) on O365. When the reset occurs, ADSS logs the attempt to sync the password to O365, but fails with the user does not exist, so it's not mapping the local AD email address field as the UPN to O365. How do I fix this? I have not (and don't wan to use) MS DirSync or AAD.