Resell of Costco purchased Items

Hi,
I wonder if anyone can assist.

I am new to Amazon and have purchased microfibre cloths from Costco, where i am a trade member, to resell on Amazon.
We are using FBA.
I listed the items and sold one unit, the received an email from Amazon asking to provide approval from the supplier to sell. They asked for proof of purchase so i sent them the receipt. This isn’t good enough.
Whilst this battle is going on-another unit has been sold in France.

I have written to the manufacturer but i can’t understand why i am not permitted to sell these items when they are already being listed by other sellers and also why i was allowed to ship them to amazon, have them listed and then be told that i cannot sell them?

Can anyone help or advise?

TIA