You would need to adjust the sort order in the citation section of the output style. Now it is probably set differently or “don’t sort” – I think setting it the same as the bibliography (which is an option) would fix it. See setting in the attached snip.
To edit an output style – there are files to download with instructions here. Make sure you “save as” to a new name, and then change the output style used in the document to the new name on the endnote ribbon in Word, or the format bibliography menu in word.