I've been using ShipStation along with ZC 1.55a for about five years now, with no problems except ShipStation's occasional bugs. Recently, I installed the new ShipStation module from the plugins. It specifically states that it works with 1.55, so I didn't expect any problems. However, although I didn't realize it immediately, ShipStation is no longer receiving a reply from the website when it tries to update the customer record with the shipping information (shipping service, date, tracking number, etc). The record is actually being updated, but ShipStation isn't getting the expected response back from Zencart that the update was successful. In some cases, there have been multiple attempts over a 24-hour period that resulted in fifteen or twenty updates to the order record.

I assumed this was a ShipStation problem, but their support people say Zencart simply isn't replying to them. Here is the communication they sent. I've obscured their password and the tracking number. Otherwise, it's exactly as they provided it to me.

GET https://www.newnaturalsonline.com/sh...rier_cost=3.49 HTTP/1.1
SS_AUTH_USER: shipstation
SS_AUTH_PW: xxxxxxx
User-Agent: ShipStation
Authorization: Basic c2hpcHN0YXRpb246c2hpcDkwMTIx
Host: www.newnaturalsonline.com
Cookie: cookie_test=this_is_a_terrible_hack
Connection: Keep-Alive

HTTP/1.1 200 OK
Date: Tue, 29 Jun 2021 21:37:37 GMT
Server: Apache
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
Set-Cookie: zenid=5d63t3svj8ugra64ndeicvjtq0; path=/; domain=www.newnaturalsonline.com; secure; HttpOnly
Strict-Transport-Security: max-age=300; includeSubDomains; preload
Upgrade: h2,h2c
Connection: Upgrade, Keep-Alive
Keep-Alive: timeout=5, max=100
Content-Type: text/xml;charset=UTF-8
Content-Length: 2