Trouble listing my unique items, any advice?

I would be so grateful for some help. I have contacted seller support but keep being sent copy paste stuff that doesn’t relate to my issue.

I made two colouring books, they are printed, physical items, no POD, no KDP, literally sitting in boxes in my house. I intend to send them to Amazon US (I am in UK) and use FBA. They don’t have branding on them, they don’t have IBANs, but they DO have GTIN-13s – not printed on, but assigned.

I paid for a membership to GS1 and assigned my books a number each. When making the listing, I am getting an error 8572 that my GTIN codes don’t match my listings, I sent them my GS1 certificates but that hasn’t resolved the issue. They ask for an official letter from the manufacturer that I can sell these books and photos of the publisher’s name on the cover – but I AM the manufacturer and I AM the publisher, they keep ignoring this and not addressing it. I haven’t registered a brand, I wanted to just list them unbranded. I applied for a GTIN exemption before becoming a GS1 member but have already had that rejected, but I have active GTINs (two weeks old) so why is there a problem?

Can anyone shed some light as to what I am supposed to do to get my listings activated? Going round in circles in seller support.

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