Could you be a bit more specific? What prevents you from entering the marks?
I would say it was a good thing that it didn't let you because what you are doing is wrong. You cannot simply enter your 1/2 yearly marks and expect to get a proper estimate. In fact, thats one of the last things I would recommend you do.
The marks from your half yearly in no way reflect the estimate given by SAM because SAM doesn't use school marks. SAM uses HSC marks which are available to students when the results come out in December.
The best thing to do right now is to look at your marks yourself. How well did you do in comparison to the rest of your class? How well does your school typically go in the HSC? Are you able to improve on those marks?
At this stage of the HSC year, you should try to steer clear of worrying yourself about what UAI estimate you'll get. It will only get you thinking more and distract yourself from more important things that you could spend your time on.
And I'll emphasise once more that entering your half yearly marks into SAM is wrong. Most likely your UAI can be at least 30 points off because it's not designed to predict UAI's based on half yearly marks. It is however extremely accurate if HSC marks are entered which are not available to the student until December.
