Sometimes a newly created debtor is not visualized in iController.
Open documents missing
In most cases this has to do with missing open documents like invoices. When creating a debtor in your (accounting) software, but not creating an (open) document, the debtor will not be transferred to iController.
As soon as the debtor has an open document in the accounting software, the debtor will show up in iController. And only after the synchronization has taken place.
Other reasons
Other reasons why the data in iController might differ from the data in your accounting software can be found here:
Why does the data in the accounting software differ from the data in iController?