If you see this error (note it could be .com/.co.uk/ca/.com.au/.de or any domain):

* Invalid seller account type.

You have signed in with an account that is not eligible for Amazon MWS. For a list of eligible Amazon seller accounts, please go here: https://developer.amazonservices.co.uk/faq.html#mwsSellers

To sign in again with an eligible account, please click here: https://sellercentral.amazon.co.uk/gp/mws/registration/register-logout.html

 

It means 1 of 2 things:

 

1) Third parties can sell on Amazon.com or any other Amazon sites as "Individual" or "Professional Sellers" but to use the Amazon MWS (the API that Codisto uses to communicate with Amazon) you have to have a Professional account.

You need to login to Amazon and look to change the account type.  This is from Amazon.com:

Upgrading from Individual to Professional Status

1. Go to your Seller Account.
2. Under the Settings heading, click the "Account Info" link.
3. On the Seller Account Information page, go to the Selling Plan section and click the "Modify Plan" button.
4. On the next page, click the "Upgrade" button.

2) Amazon has 3 regions:

Americas/Europe/Asia Pacific

You can sell on any site within a region with the same account but if you are listing on a different region you need a separate Amazon account in that region.  (This is not a Codisto issue - it is enforced by Amazon).