Once you've moved to a OneWorld account, each SmartClient user will need to refresh/clear the cache of their SmartClient as per the steps given below.
SmartClient > Options > Caching and Performance > on the Refresh button click on the drop down and click on Clear Cache (Recreate on First Use).
Please refer to the screenshot below to find these options in SmartClient
SmartClient will prompt the question for a OneWorld account and just select "Yes". For the templates, you'll just need to edit the ones that will require the subsidiary field.
Please contact Celigo Support if you have any issues in achieving this.