Error While doing GRN Due to Order Ack.

Hii All,

I am having following problem while doing GRN, Please go through the screenshots below

Order Acknowledgement Configuration, below configuration is same as standard one 0001 Confirmation control

With this config. I create PO with 10 quantity and after getting the acknowledgement from vendor I put those entries in PO as per below screenshot

After putting above confirmations, I did GRN for two quantities (1st schedule line), Now I am trying to do GRN for rest schedule lines but I am not able to do it, getting an error that GRN not possible for this PO. Even though with same configuration I created more PO's and trying to do GRN but I am not able to do.

My question is with same configuration, why system allows me to do GRN earlier and why now it is not allowing to do it same ??

Thanks

Prateek