Somehow you have a linked-URL attachment that became a standalone item. That shouldn't be possible, and it's triggering a sync error.
If you paste HSJ4U67M into the Zotero search bar in All Fields & Tags mode in the root of the group library beginning with "P", does it find an item? Does it show as a standalone attachment or a child attachment? Do you recall doing anything unusual with that item?
here it is D576109415
Thanks
If you paste HSJ4U67M into the Zotero search bar in All Fields & Tags mode in the root of the group library beginning with "P", does it find an item? Does it show as a standalone attachment or a child attachment? Do you recall doing anything unusual with that item?