Confused

Every time i try to apply or see if i am pre approved for a credit card, even a secured one, they always deny me and say i have no credit report. But i have literally looked at my credit report before.

Yeah its not great its like 600 but it could be much worse. and Ik people who have worse credit who get approved for things. I don't understand why it says i have no credit history. I have looked at a credit report with phone bills, apts ive lived in. Like what. Maybe im just 23 and stupid and dont understand anything but dang. help me