Chrome Extension – can’t change text, colors, etc on live site

I’m trying to write a Chrome Extension that simply replaces some text on a website I don’t control. (There is actually a remote lookup, etc – but let’s leave that out for simplicity.)

It works fine on my local test site. When I try to use it on the remote site; the HTML does not get changed.

I’ve searched and see everything from timing issues, to using TreeWalker, etc. I don’t think these apply as I can find the element with document.elevate(xpath…) and alert(element.textContent) works just fine.

What am I missing?

Thanks!