Sync Between Users

Hello,

I am having issues with a user I support using the To-Do app, when the user adds tasks to a shared task-list the added task will not appear for any of their colleagues, if they colleagues add a task it does appear for the user however. Similarly if they complete the task they added their colleageus will get a notification saying it was completed despite not being able to see the task. Has anyone come across this at all. I have checked the sync settings, reinstalled the app etc. This happens on the users Windows and Iphone app so it doesnt appear to be device specific.

Any help would be much appriciated.

- O