Canada post module works perfectly but only every now and then

Hi everyone,

I searched the forums and read about the connectivity issues and ports and so on. However, nothing I could find seems to apply to my case.

The issue I have with the Canada Post module is that it would display / return the information only about 3 to 5 times out of 10.
When it fails to work, the error is

"An unknown error occured with the Canada Post shipping calculations.
If you prefer to use Canada Post as your shipping method, please contact the Online Store via Email."

When it works everything is perfect - calculations and all.

I looked at connectivity and it is fine. Port is also fine. DNS resolve is OK, I tried replacing the FQDN with the IP to test and it makes no difference.

The store is Zen Cart 1.3.8a, Database Patch Level: 1.3.8, new install. The issue can be reproduced at shop.learntrapshooting.ca

Any hints would be much appreciated!

To make it easier to reproduce:

Add a small item to cart - pick the small test item in gift certificate
Estimate shipping cost
Fill in say Ontario and a postal code
Update

if nothing shows up, update again

eventually you get the correct shipping info.

If you do this via checkout, you can also see the unknown error as above.

tnx again

You'll probably have to ask Canada Post why their server isn't giving back usable responses.

Thanks - I checked with CP, they checked the logs and it looks like each and every transaction that failes to return it due to the fact that the server only receives the country - the data for province and code is missing from the request.

Where should I look?

Thanks!