Failed to fetch Stamps rates: Invalid SOAP (...) ToZIPCode element is invalid [Solution]

When processing an order, you might run into the "Failed to fetch Stamps rates: Invalid SOAP message due to XML Schema validation failure (...) ToZIPCode - The value X is invalid according to its datatype" error.

This error relates to missing or incorrect information in the order you're trying to process.

NOTE: If you're shipping to Hong Kong, note the ZIP code is 00000.

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

To solve this issue you will have to:

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. Add the Postal Code to the order 

4. Press Save to apply the changes

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