I too am having this issue. I created a PO for an item. I received the item and when asked if I would like to complete the PO, I said no. I then get a misc charge which I go back in and add to the PO and Post. I then click Receive All and add the invoice number and Post the "receipt". It asks me again if I would like to complete the order. I say yes. My PO screen still shows it as green or Partially Received. Yet I received and applied invoices to both items and clicked yes to complete.

As for "manually" completing it, my Complete button is greyed out. And yes I do have the option enabled for completing outstanding PO's.

What am I missing here? I have no other filters set up other than the defaults that are in PO.

I am using PO 8.1C (130722)