To get it working properly, do this;

Move your mouse to the top of the Firefox window, then right click. You will see a menu of the available toolbars. Select Customize. In the new window, look for the Webutation icon. When you find if, hold down the left mouse on it. Now move it to the far right of whatever tool bar you want it. It might work in other locations, but I don't know. In my case, I put it at the top of my Vertical Toolbar
(Adds a vertical toolbar at the edge of the window.) and the problem is gone.

the webutation icon is there, it's just that it's gray and doesn't light up any more to tell me 100% green, 40% red etc.

Go to the Webutation add-on page, and try installing it again. If there is still a problem, try to contact the writer.

i have reinstalled Webutation several times but W icon does not appear in new window. i understand that W is not compatible with 29 firefox. my question was how to find the installer for version 28.

I am using Webutation. At first it was causing problems. But after I moved the icon, no more problems.