I have installed OpenCart 1.5.6.4 and integrated it with this opencart-shippingeasy plugin: https://github.com/neerajskydiver/shipping-easy-opencart.

I have gone through all the steps and inputted the correct api credentials and store api key. Once I create a purchase through my OpenCart store manually, I receive the order in OpenCart, but I do not receive the order in ShippingEasy. After I confirm the checkout process, I receive this error on the success page:
Invalid response object from API: NOT FOUND
The requested URL /api/stores/{a given id}/orders was not found on this server.

I am currently using a free version of ShippingEasy (I do not think that it should make a difference) and my OpenCart store is on a subdomain on my server (it is using https).

I have spent days diagnosing this issue and I have not found a solution. I would greatly appreciate it if someone could help me out so I could resolve this issue.

Thanks,