Sad to hear you still stuck with this, but I can’t see how to help more about your specific case on the forum.
May be in a near futur... (I’m working to setup a free weekly consulting session) ;-)
You should try to create a playground (local demo, demo instance, etc) and install and experiment the profile. You may need to note each step of the installation and then try to reproduce (on a clone of your main website).
That’s what I did for and used in a Tiki19.
See the background of the video and you’ll see a functioning Tiki cart.
I believe you that there is a way to make this work, otherwise all the screenshots in http://profiles.tiki.org/Shopping_Cart?highlight=Kart would have to be fakes .
But why is it impossible to import the YAML listet on the above under "trackers" into a completely empty tracker feature? What I deem a possible explanation would be that I missed a step before importing the trackers. But if that is the case, without any error message that goes beyond "error importing" it is very hard to find out what could possibly be missing.
The only thing that comes to my mind is one of the permissions that I could not set. Anonymous shall get "list_trackers" enabled. There is no such permission in Tiki 18.5...
P.S.: Oh, I see now something before that fails, too: "feature_wiki_argvariable: y". There is no such feature in 18.5... (or it has a different name).