It depends on when you bought the item. If it’s within the last week/week-and-a-half, then your tracking number probably isn’t registering because tracking numbers are automatically generated at a certain point in the order-to-shipment process. That means that the tracking number is reserved for your item at the moment, and will only activate once the item finally ships. And remember, it was just a long holiday weekend, during which no shirts were processed or shipped. If you bought anything since last weekend, then it’s likely that you just need to be patient.
If it’s been longer than a solid week/week-and-a-half, I recommend that you email service@woot.com with your order number and a request for an update on the status of your shipment. Once in a while there’s a bad tracking number or delay, and service will be able to clarify the status of your order for you. You could also go here and put your order number into the “reference number” section, leave the “account no.” section blank, and fill the rest to the best of your ability. That sometimes works.
But, really, if you just recently ordered your shirt, please be patient.