iPhone shipment - tracking number is invalid

I had recently purchased the box to send my iPhone 11 back (its cracked). I got the box but I’m a little confused about the shipment. It says to schedule a day for FedEx to come pick up. So I go on the FedEx site and put in all the information. Then it says the tracking number is invalid. I’m not sure if I’m doing it wrong or there was already a date set for theme to come get it. I’m really not sure what to do.

[Re-Titled by Moderator]