If you receive an exception_msg=Feed rejected message during the Sync Offers operation it means that Amazon is rejecting your file. This problem depends on the fact that your account is not allowed to send such informations toward the marketplace. There can be different reasons, starting with an invalid payment method for that country (i.e. you have an expired credit card associated to your account).

You must check your account permission from the Seller Central, as there is nothing the module can do to solve this situation.