Credit score is only one factor
Credit score in itself is only a small part of the lending decision. Your Fico score may very well be good, but you probably have a “thin” credit report, meaning that you don’t have other credit other than being an authorized user on your father’s card.
Creditors and lenders look at much more than your score. They pull your actual credit reports, and want to see how you handle credit (and you don’t). It’s very common not to get approved with a high score but a thin credit report.
There are plenty of other factors that may be the reason for rejecting your application such as insufficient income, employment stability, too low down payment etc.
What you can do is either come up with a larger down payment, have your father cosign for you, or simply build your credit for a year or so and re-apply.
You can start improving your credit with secured loans, retailers’ credit card, secured credit card etc. See Building Credit History for more information.