Error while posting GR or GI

Dear All.

I am getting the below error while posting a Goods Receipt / Goods issue, Kindly suggest what could be wrong ??

"You are not allowed to post manually in the substitute system

Message no. FDM_MIRROR301

I am trying to post the GR against a standard PO and trying to make GI against standard outbound delivery

Best Regards,

Santosh Kumar B V