New emails not appearing in 'inbox' view but visible in 'unread' view.

New emails not appearing in 'inbox' view but visible in 'unread' view.

One of my user email accounts is experiencing an issue where any new emails received are not showing up in the 'inbox' view in the Zoho Mail web client. I instructed the user to use the 'unread' view which appears to show all new emails. This started to happen from 30 November. How can I get the user to view new emails in the 'inbox' view?