This error message may occur due to several reasons, here are a few possible solutions:
Check if the path to the Excel file is correct. Make sure that the path you have provided in the “Append Range” activity is correct and the file exists in that location.
Check if the file is open in another program. Make sure that the Excel file is not open in another program. If it is open, close it and try running the process again.
Check if there are any invalid characters in the sheet name. Make sure that the sheet name provided in the “Append Range” activity does not contain any invalid characters such as “?”, “*”, etc.
Check if the sheet name is case-sensitive. Make sure that the sheet name is spelled correctly and that it is case-sensitive.
Check if the format of the data is correct. Make sure that the data you are trying to append is in the correct format and that it matches the format of the existing data in the sheet.
Check if the data table has any null values. Make sure that the data table you are trying to append to the excel sheet doesn’t have any null values.
Check if the datatable has headers or not. Make sure that the datatable you are trying to append has headers or not as per the sheet.
Check if the sheet is protected, you will not be able to append data to a protected sheet.