Hello Wang,
As per standard GR cannot be performed by user for below reasons.
1) GR already performed for full quantity and No Further Confirmations selected.
2) PO is having some errors in SRM system pertaining to posting date
3) Other users without super user role.
I hope as per checking the discussion above, first 2 points are addressed.
I am with the 3rd point , whether you are having super user role or not to perform confirmation.
If PO creator is not able to perform confirmation , then it is an issue.
I am thinking this would be an authorization issue. please check in that view.
Thank
Gupta