We're so sorry to hear about the trouble. As per the screenshot you are on https://assets.adobe.com/files so any files that are synced here are also available on your computer in the Adobe Creative Cloud file folder. So please navigate to the Creative Cloud files folder and try accessing the file. Let us know if that helps or if you need any further assistance.
As I noted in my original post, local creative cloud folder sync is not an option for me at this time (it takes up too much space on the computer in question and it becomes unusable).
I need a way to access the file via the Assets section of Creative Cloud web. The file is there. There is no reason I shouldn't be able to download it, when I have edit permissions to this folder. Why has Adobe disabled downloads of XD files from CC web? What is the workaround that doesn't involve local file sync? If Adobe were to enable selective local file sync that might be a good solution for me, but I can't sync our whole library.