Chase Freedom Unlimited applications could be denied because of a low credit score (below 700), not enough annual income, or too many recent credit inquiries. Other grounds for denial could be incomplete or inaccurate information on the application, or a pending bankruptcy on your credit report.
Whatever the reason, Chase will send a letter detailing why you were denied for Chase Freedom Unlimited within 7 to 10 days of rejecting the application. You can use that information to help determine your next steps – requesting reconsideration, applying for a credit card that's easier to get, or building your credit as an authorized user on someone else's account, for example.
On the other hand, if you already have the Chase Freedom Unlimited card but were denied when you tried to make a purchase with it, it's possible that the card hasn't been activated yet or you've exceeded your credit limit. If this occurs, first have the merchant try the card again to confirm it's not an issue on their end. If the transaction is still denied, contact Chase customer service at 1 (800) 432-3117 to determine the specific reason(s) why the transaction didn't go through.