
How To Configure Amazon Selling Partner Permissions
Configuring your Amazon Selling Partner API (SP-API) user permissions in Seller Central

To authorize the Amazon Selling Partner API application, your user account must be either;
The primary seller account or;
A secondary user in your seller accounts with admin permissions.
If you are using a secondary user to authorize, please make sure any secondary user account has "Admin" permissions. If permissions are not set correctly, Amazon will reject our authorization requests with "Invalid Access" errors.
Here is Seller Central with a permission error;

If your user doesn't have the right permissions set, we won't be able to collect data for you. User permissions must be set properly for Amazon to allow access to the Selling Partner API.
How To Set up Secondary User Admin Permissions
The Amazon interface may vary slightly from one seller to another.
Seller Central
For Seller Central, you will want to ensure the user has Admin where applicable in your Seller Central interface. Here is an example:

We hope this clarifies your question.