SELECT [CA].[RepObj], MAX( RF.Date ) as [RfidDate]
--FROM...
GROUP BY [CA].[RepObj]

SELECT tb1.[RepObj],  tb1.[PressForm], tb1.[Date]
FROM(
    SELECT [CA].[RepObj], 
            RL.[Asset] AS [PressForm], 
            RF.[Date], 
            ROW_NUMBER() OVER(PARTITION BY CA.[RepObj] ORDER BY RF.[Date] DESC) AS R
    -- FROM ...
) AS tb1
WHERE tb1.R = 1

SELECT [CA].[RepObj], RL.[Asset] AS [PressForm], MAX( RF.[Date] ) as [RfidDate]
 -- FROM
GROUP BY [CA].[RepObj], RL.[Asset]

SELECT [CA].[RepObj], RL.[Asset] AS [PressForm], MAX(RF.[Date]) OVER(PARTITION BY RF.[Reader]) AS [RfDate]
--FROM

SELECT [CA].[RepObj], RL.[Asset] AS [PressForm], MAX(RF.[Date]) OVER(PARTITION BY RF.[Reader]) AS [RfDate]
FROM [table1]  AS [CON]
LEFT JOIN [table2] AS [CA] ON CA.[Client] = [CON].[Oid] 
LEFT JOIN [table3] AS [RR] ON RR.[Asset] = CA.[RepObj]
LEFT JOIN [table4] AS [RF] ON RF.[Reader] = [RR].[Oid] 
LEFT JOIN [table5] AS [RL] ON RL.[Oid] = [RF].[Label]
WHERE CA.[Active] = 1