I have been successfully using a script to export selected records in Excel format from FM12. The resulting XLSX file has been used to mail-merge data into a Word document.
After upgrading to FM15 Word is giving me an error message that it cannot open the XLSX file. By luck, I found that if I open the file with Excel and do a Save-as the resulting file will open in Word.
It seems that something has changed in the File/Send-records-as/Excel function that produces an XLSX file that Word is unable to read.