SAP B1 blocking query

Hi experts,

May I inquire wherefore is my query blockings successful SAP B1 is not moving if I see @OpenAmount adaptable successful my condition.

the query volition posted below:

IF (@object_type = '1470000113' AND  @transaction_type IN ('C', 'L'))

BEGIN 

DECLARE @OpenAmount NUMERIC (20,6) 

,@Footer nvarchar (32),@cancelled nvarchar (1)

SELECT @Footer = A.U_Reason , @Canceled = A.CANCELED, @OpenAmount = SUM (B.OpenSum)

FROM OPRQ a INNER JOIN PRQ1 B ON A.Docentry = B. Docentry 

WHERE A.DocEntry = @List_of_cols_val_tab_del --AND ISNULL(A.U_Reason,'') = '' --AND  A.CANCELED = 'N'

AND a.DataSource <> 'O' 

GROUP BY A.U_Reason, A.CANCELED, B.OpenSum

IF  @Footer IS NULL AND @OpenAmount >= 1  // (This adaptable openamount is not work successful SAP B1)

BEGIN 

SET  @error_message=N'Provide crushed for Closing/Cancelling past Click Update first'

END 

END

Thank you