"Cannot get mail" Zoho is currently unavailable

"Cannot get mail" Zoho is currently unavailable

All of the email accounts I have get this error on iOS devices yet all accounts can login via a browser so I know that passwords are correct. Accounts were working fine on all devices until a week or so ago. I am using my own domain and using "imappro.zoho.com" for the incoming mail server. How can the mail be working (I know this because of logging in via a browser) but I can't use it with other mail programs?