So read the forum and it is not popping up for me either. I went to the USPS site and it was going to cost me $22.10 to ship it from there. I had an idea and cut the glued flap from the inside of my flat rate box and turned the box inside out and taped the flap back into position. Now, none of the "Flat Rate Box" writing is visible and it looks pretty much like a standard box with some writing regarding Priority Mail Service. That same box cost me $9.60 to ship from Shopify. I will let you know if I get kick back out of it, but I don't really see why I would.