Doesn’t ecwid have a Wix App you should use instead? You can’t paste in HTML code or Javascript into Wix Code and it will work like any HTML page editor. Wix Code has a special API and you will read some beginners tutorials on this first here I would suggest.
If you don’t want to add the ecwid Wix App from the Wix App Market drag out a HTML Iframe component and paste in the code inside that one.