The Amazon authentication process is different for connections to marketplaces outside of the Americas. And it's required that you install a separate copy of the MCF integration for each marketplace outside of the Americas. Here's the recommended steps.
1) Logout of seller central and pipe17
2) Start an incognito window or other private session in a supported browser and login to pipe17
3) Add a new MCF integration and login to seller central in a new incognito tab
4) Authorize the connection
5) Setup the MCF integration to pull locations and pull inventory, leave push shipping requests off
6) Wait 5 minutes and verify you have inventory
7) Repeat steps 1-6 for the other marketplaces outside of the Americas
8) This process may result in extra locations that make the user experience difficult to navigate. Look at your inventory page and see which locations have inventory. Update the locations to "Inactive" status if they do not have inventory and you do not expect to inbound inventory to that location (marketplace). This may be easier if you use two tabs in your browser, one for "All Inventory" and one for locations.