Originally Posted by
zcat18
So I guess the moral of the story is that I should keep trying, even if the odds are against me. Perhaps it will work one of these days.
No, the moral of the story is to try to book flights with open NC or NF space and confirm immediately. Don't just hope it will work out.
If NC or NF is available status does not matter. That said, as others have pointed out, with UA holding back upgrade inventory it has become more difficult.