Am gussing it has something to do with the From or To LSN values, do you get any data back if you run this query directly against the CDCDemo database, this should verify that the change table is returning data:

DECLARE @from_lsn binary(10), @to_lsn binary(10)

SET @from_lsn =

sys.fn_cdc_get_min_lsn('dbo_contract')

SET @to_lsn = sys.fn_cdc_get_max_lsn()

SELECT * FROM cdc.fn_cdc_get_all_changes_dbo_contract( @from_lsn, @to_lsn, 'all')

GO