Unable to Add Alias Address to Admin Account after Getting a Second Domain

Unable to Add Alias Address to Admin Account after Getting a Second Domain

I'm trying to add jcullen@hellospeechtherapy.ca to the admin account of zoho mail. however, it says Unable to add Alias Address.

I have been contacting support for over 4 weeks about this issue. I kept getting emails saying the issue was fixed but it never worked.