Cart not shown when created by webservice

[covis]

One of my customer keep asking me to move his shop to wordpress (facepalm, I know).

He's more into it and already bought themes and stuff.

 

Since I'm not the only developer working on this project, some wp-guys fulfilled his wish and built a wp-site.

However, they still use PS as checkout and payment tool. The communication is done by webservice of PS.

 

This week I got a call from them, where they wanted to know why the cart they created by webservice, is not shown, when they redirect to the cart of PS?

It seems they put the right customer id into the xml-string, and the backend shows the cart properly.

 

Any help?