USPS Priority Mail To Canada Is Not Displaying

[seattletechworks]

Preconditions

1. Magento 2.1.7, PHP 7.0.20, Nginx 1.20.2, MySQL 5.6.34-79.1
2. Set up and enable USPS for checkout under admin panel:
   Stores -> Configuration -> Sales -> Shipping Methods
   Allowed Methods should include First-Class Package International Service and Priority Mail International.

Steps to reproduce

1. Add a product to your cart which has a weight of more than 4 pounds
2. Go to the cart page - Example https://www.yourstore.com/checkout/cart/
3. In the Estimate Shipping and Tax section, enter these values:
   Country - Canada
   State/Provide - British Columbia
   Zip/Postal Code - V8G 4R6

Expected result

1. A live quote from USPS for Priority Mail International should be returned

Correct rates are displayed for other countries. For example, specify these values to get a positive result:
Country - Australia
State/Provide - NSW
Zip/Postal Code - 2000

Additionally, if the product weight is 4 pounds or less, the correct First-Class International service quote is displayed for Canada. The issue only occurs with Priority Mail International quotes.

Actual result

1. A message in the Summary box displays: "Sorry, no quotes are available for this order at this time"

Error from ~/var/log/debug.log file:

The Origin ZIP Code and the Destination Postal Code is required for ECOMPRO when mailing to Canada.

Other comments

I found a similar defect from March - #8041

[veloraven]

@seattletechworks thank you for your report.
We already have a fix in develop branch, you can find it in commit 69a0f5c from the PR #8041

[korostii]

Hi @veloraven, I see that you've added a needs update label.
Would you please care to explain what kind of information you need from community in order to proceed with backporting an existing fix to the 2.1.x branch?