Can't add Tracking Number

[memorylanetelephones]

I entered a bunch of tracking numbers but one of them won't take. I enter the number, select USPS, then "Save" and when I go back to "Manage orders waiting for shipment", it's still there. I've tried numerous times over the last couple days, it will not take.

[calntom]

The only thing I can think of is to make sure there are no spaces before or after the tracking number