Hello,
Check the application log by SLG1, it will shows the document category,
then goto OACT and see the content repository of this.
The error should be caused that the corresponding document is not existing in
the content repository, you may need to check with your application consultant
on where the document was stored. If they were indeed stored to the same repository
as OACT and the document has disappeared, you may check if there is any backup of
the document.
Regards,
Wen Peng