Thanks for the thorough report @LaurenBurchell, it definitely sounds like everything should be working given your setup.
Could you go into a bit more detail about which cards are not syncing? Do they have anything in common with either the way you created them or their content? Feel free to message us via the in-app messenger if you’d like to keep that info more private.
I’m having sporadic issues with syncing collections as well and opened another thread about it. The consistent error seems to be an HTTP POST error about an h process able object --this happens when I attempt to change collection details in the web app. The changes then appear locally in the web app but don’t seem to sync to other platforms.