Hi Saurav,
Message not OK means document is not OKwith the dynamic credit check and the odest open items credit check. It means document has exceeded dynamic credit check limit which is given to payer customer and same is the case for the oldest open items credit check.Hence the document you are checking is blocked for credit. If you check the sales order in the header credit status will be not approved means document is blocked for credit.
Further the the payer customer what system had analyzed in CHECK_CM report (First screen shot 100547) is different from the FD32 screenshot what you have attached (second screen shot 101728).
Please check the 100547 customer for ZKAL credit control area in FD32 screen which will give you the details of the credit limits used.