I had been having the SAME issues you have that when I run Checkout Wizard, NOTHING HAPPENS. I have uninstalled and reinstalled the extension numerous times, but nothing happens.
Also, when I load up an eCart site in Dreamweaver that I KNOW has an eCart object on it, the eCart panel doesn't register it. I can't select a cart and clicking "add" doesn't do anything.
Sound familiar? Here's what worked for me. YMMV.
No amount of reinstalling or installing the extension worked. But this did:
1. Close Dreamweaver.
2. Open Adobe Extension Manager. DO NOT "remove" the extension, simply toggle it on/off.
3. Once you get confirmation that the extension has been disabled, then..
4. CLOSE Extension Manager.
5. Start Dreamweaver. (Note there is no eCart menu panel now.)
6. Load a site. Any site.
7. CLOSE Dreamweaver.
8. Open Extension Manager.
9. Toggle eCart extension back to "on".
10. Close Extension Manager.
11. Re-open Dreamweaver.
12. Load an existing eCart site, or create a new one.
13. Voila'. I was then able to select eCart objects, create them, and even run the Checkout Wizard.
Hope this helps anyone out there struggling with this little issue, because it is very, very real.
And for the record, I don't know if this caused it, but my extension worked beautifully until I deleted the eCart folder in the site directory FROM within Dreamweaver. I wasn't able to build any other eCart objects after I did that. May be a coincidence.