The server imap.zoho.com has sent the following alert:

The server imap.zoho.com has sent the following alert:

The past 2 days i have the following message on my blackberry 10 device:
'The server imap.zoho.com has sent the following alert: "You are yet to enable IMAP for your account. Access the link https://www.zoho.com/mail/help/imap-access.html to learn more. (Failure)." Please address the issue with your IMAP service provider and try again.'
I have confirmed that imap is enabled but still the message arrives. I have a number of email accounts and only 1 is affected.Web mail for this account is unnaffected and is working fine.
What is the solution please?