Hi Anne,
I know that this is an extremely common problem experienced by those doing the
SCJD assignment (even has a
FAQ Answer). My guess is that they only set one state for anyone's prometric login. At present your state is set to "download", so you cannot upload (you can download multiple times though - some of us found that we could get two different SCJD assignments that way

).
Anyway, when you got that message, it should have included an email address to write to so that you can get this fixed. Most people have reported that they got an email stating that the problem was fixed within 1 working day of reporting it.
At least for the SCJD if you have reported the problem (via the specified email address) and then sit for the exam before you can upload the assignment, you are not penalized.
Regards, Andrew