You may receive the error "Excel cannot open the file 'xxxx.xlsm' because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file." when exporting to Excel (xlsx) with a file name that has the extension xlsm.
Sync & Save can export to an existing xlsm file, but does not create a valid xlsm file. If you need to export to the xlsm format, please use Excel to create an xlsm file first, and then populate it with Sync & Save.