Ok, a bit strange, above all if it worked from Xbox to your steam deck.
Just to verify if it (still) work from xbox to your steam deck :
- On your steam deck, create at least two (new) manual saves in a raw to be sure to not loose your progression.
- On your xbox, load the last save you have on it, create a new manual save and wait a bit to see if this save is uploaded (checked cloud icon).
- If the save is well uploaded, verify on your steam deck if you see it.
If you see the save newly created on your Xbox, well there is definitely something which doesn't work in the other way. Unfortunately, I don't see why it wouldn't work

So your best bet should be to directly contact the support ("contact us" button). Provide as much details as possible (even the link of this thread).
There is no dedicated category, but this one should be fine :
Welcome to CD PROJEKT RED Technical Support! Here you will find help regarding our games and services, as well as answers to frequently asked questions.
support.cdprojektred.com