My account has been deactivated, but I don't fully understand why

As @Seller_rI7BZIczK8iACnotes, you need to prove authenticity BUT it is also possible it is something else.

Do you have an LOA from the BRAND? More and more brands are restricting sales on here and THEY can tell Amazon that no one can create an ASIN.

Here is a lengthy discussion that might have some insight to the Amazon terminology (it's a template and some parts may not apply) --

From @Atlas_amazon

(EMPHASIS ADDED PARTS)

For your sourcing, you mention acquiring product directly from the brand, do they also provide to you a letter of authorization? This document would need to explicitly state you have permission to list the product on the platform. As seen in our anti-counterfeit policy, inauthentic product can be product that has not been given explicit authorization to be listed on the platform.

If you have any additional details to share or questions regarding how to proceed, continue to refer here for support.

Best,

Atlas

The anti-counterfeit policy can be found here:

https://sellercentral.amazon.com/help/hub/reference/G201165970

UNSUITABLE INVENTORY POLICY

https://sellercentral.amazon.com/help/hub/reference/GH4YYXNDRW9BSZEN

Unsuitable inventory investigations policy

Customer trust is paramount to Amazon, and we strictly prohibit the sale of counterfeit products and other illegal goods. If we find that you have engaged in the sale of such goods through our fulfillment network, we may deactivate your account and offers, consistent with section F-7 of the Fulfillment by Amazon Service Terms in the Business Solutions Agreement ("FBA Service Terms"). We may also withhold and/or dispose of your inventory in order to protect our customers and sellers.

Amazon will notify you if we require additional information about inventory that we have determined may constitute Unsuitable Units under the FBA Service Terms. If your inventory is withheld due to suspected violations of our anti-counterfeit and restricted products policies, we will notify you by email and conduct an investigation.

As part of this investigation, we may request that you provide additional information or documentation regarding your identity, product authenticity, and compliance with applicable laws. We may validate any information that you provide with third parties or government agencies. We may withhold some or all of your inventory while we investigate.

If you do not provide the information we request by the stated deadlines, or if we find that any of your inventory constitutes Unsuitable Units, including but not limited to as a result of fraudulent or illegal activity such as the sale of counterfeit products or illegal goods, the violation of Amazon’s anti-counterfeit policy, or submitting forged documents to Amazon, we may dispose of any such inventory immediately, in accordance with the FBA Service Terms. If we determine that your inventory has not violated this policy, we may release the hold on your inventory or allow you to request that it be returned to you.