Do you have two windows of "maintain purchase orders" open? If so, you'll be able to work in one window but the other will be grayed out.

sounds like experience is talking here.   After trying the 2 windows open, on the same PO #,  I can reproduce the ICONs that are grey out on my machine

I didn't have two windows open, but I suspect someone else in the building may have had one open and forgot about it. I was able to access the PO after about an hour. I imagine they realized it was open and closed it. Thanks!

I believe ESCOPAM was correct with their answer.  The screens will be grey is the same window is opened more than once.