Overview:
When the mouse is hovering over a Document Notification, an error occurs: Object not Found.
Root Cause:
The hovercard is looking for a version of the document that no longer exists.
Solution:
This is currently working as expected. This function looks specifically for the version that is created with the notification. If that version is deleted, or if it was up-versioned in a workflow, the hovercard information does not appear in that notification. Click the link to navigate to the document.
Related Documentation:
Vault Help Documentation: Notifications