Couple of things on this as i went through the same thing:

- The letter they send you states a reason why they could not approve you. If the reason was that your SSN "was not valid" (my case), you CAN call them up and send a copy of your SSN to them. I got rejected at first but then approved after i sent them a copy.

- If you want to check your credit on creditkarm per example, you will have to wait a couple of months after you get your SSN. It just takes a bit of time before they recognize your SSN and starts tracking your credit.

- Don't go applying to 5 different credit cards as all that will impact your credit history. Like somebody else said, if your parents have a CC already, just apply to be a "dependent". You will most likely get approved.

- Obviously, having a job will impact the decision on whether you get approved or not. If you don't have a job, a secured credit card is your best bet to start your credit.