Cannot publish/unpublish items

-- url of the page with the problem -- : sterlingreputation.com
-- HikaShop version -- : 4.4.2
-- Joomla version -- : 3.9.26
-- PHP version -- : 7.3.23
-- Browser(s) name and version -- : Edge (latest) Chrome (latest) Firefox (latest)
-- Error-message(debug-mod must be tuned on) -- : the system does not return an error

When we try to "publish" an item on the product screen by clicking the toggle, the red "X" disappears, but the green check mark does not appear. The item is not published.

If we open the item directly, and try to publish from the item entry form, the system errors out. No error is displayed, even with maximum error reporting turned on.

This is a new error since loading Hikashop vers. 4.4.2. It occurred after 4.4.2._2021-04-29_13-35-39, and continues to happen after uploading the patched version 4.4.2_2021-04-29_19-27-26

It happens on all browsers. We have checked the database and recompiled - it still happens.