If you are getting a seller token error, this is due to authorization in Amazon expiring.
If you are getting a seller token error in Amazon and the integration has never worked before please visit the steps in Amazon Store Integration to connect your account.
You must have an Amazon Seller account on the Professional plan to use this feature. If you recently downgraded your Amazon plan to an Individual Seller plan, it will not allow you to renew user permissions.
If this integration was previously working, you will need to reconnect your Amazon integration with the steps below.
Renew your Amazon Authorization
Select the Dashboard tab.
Scroll to the bottom to Ecommerce Integrations and select your Amazon integration.
At the bottom select Reconnect Integration.
A new tab will open. Sign into your Amazon Seller Central account.
Once you are signed into your account, Amazon asks you to agree to grant Webship access to your Amazon account.
Check the box next to the "I direct Amazon to provide Webship access..." statement and click Confirm.
Next, you will see a message that you have successfully updated the Amazon app. Select Start Shipping.
The system may take a few minutes to update after authorization.