Trying to list product, losing my mind

I am a manager for an electrical supply company, mainly commercial and residential construction materials. I have had some moderate success selling a number of breakers through Amazon already, so I am familiar with the process of getting authorization from manufacturers and generally how the process is supposed to proceed.

We have a large stock of potlights that I am currently trying to list for sale. They were purchased overseas from a manufacturer who, at our request, made the box with our company colours and brand name. We operate under said brand name and have a registered company number here in Canada for this purpose.
As well, I have paid for a GTIN number with GS1 Canada.

When I initially applied, I was told I need authorization. I receive error 5461, and am told to reapply after sorting the matter with GS1. I get error 8572, and am told I need authorization from manufacturer. I provide the authorization, reapply, and am told that the GTIN doesn’t match what GS1 is saying.

I genuinely feel like I’m missing some key component in the process, and I’m hoping someone would be able to point it out. I feel like I’m being shuffled off from one tech who doesn’t want to deal with the issue to another. I also am doing this in a vacuum, so I’m not sure how common things like this are.

Thanks very much for reading, I am happy to provide as much input as I can via DMs or here.