Change MAX(transactionid) to MAX( Value ) in your query

The below method is another way to accomplish the same

SELECT TT.TransactionId,

MAX( CASE WHEN TT.name = 'CreatedBy' THEN TT.Value ELSE NULL END ) AS CreatedBy,

MAX( CASE WHEN TT.name = 'CustomerId' THEN TT.Value ELSE NULL END ) AS CustomerId,

MAX( CASE WHEN TT.name = 'Accno' THEN TT.Value ELSE NULL END ) AS Accno

FROM TransactionTracking AS TT

GROUP BY TT.TransactionId