OPENPYXL get_column_letter not working with exported PANDAS dataframe - any help? :)

Question

I am taking data from a workbook using PANDAS and then exporting it into a new workbook. This is working as expected. When I create a table using OPENPYXL I usually use the following code:

table = Table(displayName="Table2", ref="B1:"+ get_column_letter(data_sheet.max_column) + str(data_sheet.max_row))

However this isn't working as my get_column_letter & row is returning 0. Here’s how I'm writing to excel:

pd.to_excel(destination_file_name,sheet_name="Sheet3")

Am I doing something wrong while writing to excel??