Shopify USPS prepaid postage not scanning at post office

[Mcflyy636]

Has anyone had an issue purchasing prepaid postage through Shopify and the post office is unable to scan the barcode?  They have to manual type in the number and then notify me it probably won't be updated during transit.

I know it's not my printer as I turn in prepaid postage from Etsy all the time with no issues from the post office scanning the barcode.