Did you try to save in .doc or .rtf? To be sure that you do not loose any information, you might resave the original in 2016 and then compare the resulting file with your client file prior to translating the "downgraded" .doc or .rtf.
Mike Roebuck wrote:
Thanks for the tip. I checked the docx file properties and it's set to open with Word 2016, which is what I'm using.
I tried your suggestion, but to no avail. I still can't open the file in Trados and am still getting the same error message. Unfortunately, this means I can't try the second of your suggestions, either.