From the Mailings tab, select 'Start Mail Merge' and change the merge type to 'Normal Word Document', then save the document. Then from the same tab, 'Select Recipients' then 'Use an Existing List'. Browse to the folder where the Excel data file is stored. Select the sheet with the data and click 'OK'. This will set the merge type to 'Letters'. Save the document again.
If this doesn't work, it suggests a problem with your data source. Try re-copying the original to the new location.

__________________
Graham Mayor - MS MVP (Word) (2002-2019)
Visit my web site for more programming tips and ready made processes www.gmayor.com