Failed to fetch pitney bowes rates: Exception of type (...) 1021003 - Invalid/unsupported GU countryCode [Solution]

When processing an order you might come across the "Failed to fetch pitney bowes rates: Exception of type 'PitneyBowes.Developer.ShippingApi.ShippingAPIException' was thrown.

1021003 - Invalid/unsupported XX countryCode" error.

This message is either shown when the Country and/or State Code is incorrect, or when shipping to an APO/FPO/DPO, or US Territory, the state is invalid. 

NOTE: Take into account that USPS considers Puerto Rico and Guam as states instead of Countries.

Feel free to follow the step-by-step guide written below or the video guide, as you prefer:
 

To do so:

1. Find the order through any of the possible ways (after Import Orders, Batches, Order History, etc) as it applies to the case
 

2. Click the edit button of the order you wish to change

3. Correct the Country and/or state in the order (the Country if it's a APO/FPO/DPO or US Territory case, changing the Country and using the previous country as the State in this last case)

4. Press Save to apply the changes

If the rest of the order information is correct you will be able to process it.