Outgoing mail disabled for no reason

Outgoing email for our customer-facing email address "emporium-at-kittenblade-dot-com" has been disabled for two days, for no reason. We are unable to re-enable outgoing mail; attempts to do so result in a pop-up message "Operation permitted for paid user(s) only."

Email to "support-at-zohomail-dot-com" regarding this issue has been ignored. This is unacceptable. Please re-enable outgoing mail for this account, and reply regarding the reason this happened in the first place.

This has also been submitted as a support ticket at https://help.zoho.com/portal/zohocorp/newticket

[Edit: obfuscate email addresses to thwart spam harvester bots]