Description
If the Schema Type parameter is set to Input schema must match target schema, input feature classes or tables must have the same schema.
Solution
Make sure all the input feature classes or tables have the same attribute schemas. If the schemas are not the same, you can set the Schema Type parameter to Use the Field Map to reconcile schema differences, so only those fields and their values in the input that match fields in the target dataset are used. See the Append tool documentation for a more detailed explanation.