XD files usually not sync via CC desktop app.
XD files only sync when I save them as a new file. Niether XD files can not be downloaded from the cloud web platform, however I see there the relevant, latest state.
Ricardo Pinto commented
If it would be possible to allow us to Download XD files from the assets.adobe.com website, we would at least have a way to get the updated file from there. Add the download button for XD files. Basically all the other file formats allow download already