check the datatypes for the fields in the sheet which you appended to the existing data source.
It might be the existing fields have different datatype and the appended data has different data type.
Try creating a new datasource with old as well as new appended dataset. If that works replace the old datasource with new datasource which solves your problem.
Checked the datatype. but nothing works out. It is as same as the old format / data type.
Thanks. But it didn't help me out.