output type problem for transaction MRKO

Hi,

Transaction mrko should create invoice & post invoive document to spool.

When i execute the transaction with mat doc i can see invoice document created but can’t see layourtin spool.

But i can see layout when i execute mr91 output message types with processing mode 1 (processed without error).

Layout is processed without error but not in spool why?.

Similar transactions mrrl, mris when i execute i can see layout in spool but not mrko.

Pls suggest guys what to do to see layout in spool.

Thanks for all your help in advance.