When you are using https://graph.microsoft.com/v1.0/drive/items/{item-id}/workbook/worksheets/{worksheet-name}/tables/{table-name}/rows/add
this graph endpoint is checking that file on default site.
Since this item is not present in default site you were getting this error and this POST https://graph.microsoft.com/v1.0/sites/{site-id}/drives/{drive-id}/items/{item-id}/workbook/worksheets/Sheet1/tables/table3/rows/add
endpoint its working fine.
You can also use POST https://graph.microsoft.com/v1.0/drives/{drive-id}/items/{item-id}/workbook/worksheets/Sheet1/tables/table3/rows/add
Graph API endpoint where drive-id is the Specific site drive-id where item is present.
Hope this helps.
If the answer is helpful, please click Accept Answer and kindly upvote. If you have any further questions about this answer, please click Comment.