Hello,

Although we are not able to debug your code, I can tell you for certain that your LABKEY.Query.updateRows() call is correct based on our documentation.

https://www.labkey.org/download/clientapi_docs/javascript-api/symbols/LABKEY.Query.html#.updateRows

If you are receiving a message stating that "Existing Row Not Found", then that row definitely does not exist. I would recommend you access the list in question and be sure to expose all of the columns in your grid view, including the Key column and confirm what row values you have for the Key column. It is likely that this particular row was deleted and if you had tried to re-input the row and your list is setup as an Auto-Incrementing Integer, the Key column value would be different for this newly re-entered row.

Regards,

Jon