Error:

Feed Rejected - InvalidMarketplace

Reason:

This is an error from Amazon because either your Amazon account is brand new or your Amazon account has become inactive for some reason.

Resolution:

To resolve this issue, please login to your Amazon Seller Central and re-submit your credit card/ banking financial details.

We've observed that this error usually goes away within 2-3 days after re-submitting your financial details on Amazon Seller Central [since it re-activates your account].

If you've just recently opened an Amazon Professional Seller Account, then you'll have to wait for about 2-3 days in order for Amazon to completely setup your account.

If problem still persists:

If you're still experiencing the same error, after waiting for 2-3 days, then please create a case with Amazon Seller Central so that they can assist you further.