Live Chat code created in Salesforce not displaying in Marketo LP edit mode

Does it appear on the preview or the approved live page? There is a lot going on behind the scenes in the email editor so if your chat uses script or something it think this is understandable.

What is the URL for the landing page?

It may be a jQuery conflict. If you are using Chrome you can quickly identify problems clickking the main menu on the top right corner, click Tools and then select JavaScript Console.
The Developer menu in Safari has similar tools.
Firefox requires Firebug, a freely available plugin similar to Chrome and Safari's native tools.