How to use Word upload in Print/Merge function?
Which of the various Print/Merge windows are you using - ie what steps do you take to get to that window?  (Similar-looking print/merge windows use different code so the functionality is not consistent.)

It sounds like you are doing the right thing - ie create a Word doc with the tokens and upload it.

Do you mean that some of the tokens work, or none at all? If so, which ones do and don't work? It depends on the context as to which tokens are available so I'd start by creating a simple test using the on-screen composer to check that the tokens are being evaluated correctly in that context.  If they don't work there, they won't work in a document.

Be aware that the functionality with documents can produce poor results if there is complex formatting since the document is converted to html and so depends on the capability of the conversion library.  You might find that converting to ODT produces better - or worse - results compared to DOCX.

In a recent project, we concluded the best option was to do the conversion to html outside of Civi and paste it into the on-screen composer window using the 'Source' button.