Check the dentist is active for the date range you are running on the UDA report - if the dentist is marked on the contract as 1/4/2011 to 20/4/2011 but has TC'd UDAs on the 21/4/2011, these will not show as it looks at the contract dates.  You can check the dates in File - PCT Contracts, double click on the contract and double click the provider.

Check the dentist is not marked as a VT - if a dentist is marked as a VT, the UDAs do not go towards the contract and do not show on the report.

Alternatively try to run the old UDA report instead as this tends to show much more accurate figures.