This is a known glitch at Etsy. One of many that Etsy Labels has had. I use Pirateship, which rarely has problems, and when it does, you can reach a Tech person in 2 minutes and they can usually solve your problem in less than 5 minutes, instead of waiting days or weeks for Etsy Help to reply.
It is well worth paying your postage separate from Etsy. Not really a big deal. Transfer your money from Etsy to your bank account, then set up Auto Pay at Pirateship for whatever amount you want, and they will automatically make a withdrawal when you need more postage. You set it up once, and then all your orders transfer to Pirateship, and when you buy the label, it automatically posts the tracking number back to etsy when you purchase a label.
Some of the postage is cheaper, too, especially foreign postage, and they also have UPS at a 70% discount that is often less than USPS charges.
