There are plenty of counterfeit items sold through shonky wholesalers and most of them are happy to tell you they will authorise you to re-sell.

It is very difficult to get a suspension lifted after that type of accusation and talking to a lawyer will just cost you more money, ebay have a legal right which is included in their terms and conditions to suspend or close any account they wish for any, or no, reason.

I should think your only hope would be to get your stock examined by the brand owner and then produce a letter from them saying your stock was genuine and that you were authorised to sell.

Usually for ebay to actually suspend a seller it is because the rights owner has reported the items as fake.