Hi
The issue has been resolved. After trying multiple times, the answer (however weird) was to link my game to itself.
For those encountering the same problem, on the Steam version, click on your ID in the top left and check your links.
In my game, the Steam link was not ticked. so I had to click on it to generate a code, and then head back to the options screen and click link device and enter the code. Basically, to link the desktop version to itself.
Weird workaround, but it works. So I'll leave this up here for others with the same problem.
Summary: Ensure all the links (Steam, Asmodee and Gamecenter) are all checked. If not, link the ones that are not checked.