Can you check whether it is disabled in Firefox?

orange Firefox button or Tools menu > Add-ons > Extensions category

The extensions are in two alphabetical groups: first the enabled ones, then the disabled ones. Can you find the Cox toolbar?

If it's enabled but not visible, you should be able to display it using

View menu > Toolbars

If you have the orange Firefox button, tap the Alt key to temporarily display the classic menu bar.

If it's disabled, can you Enable it, or is it marked as incompatible?

If it's not listed at all, have you restarted Firefox since doing the installation?

It is showing a yellow info that Cox Toolbar is incompatible with Firefox 5.0. It is also showing that Cox Toolbar 1.0.0.20 -PROD (disabled)

When Firefox disables an add-on, it usually is because it includes a list of compatible Firefox versions and it hasn't yet been updated for Firefox 5. (Cox didn't mention this??)

Is this add-on important to you? If so, here's a possible workaround.

If the toolbar worked on Firefox 4, there is a good chance it will work on Firefox 5, but no guarantee.

You can force Firefox to ignore add-on version restrictions by (what else) installing an add-on.

Add-on Compatibility Reporter :: Add-ons for Firefox

After you install this add-on and restart Firefox, there will still be a message that "--- is incompatible with Firefox 5.0" but the add-on will be enabled and a Disable button will appear for that entry. Then you can test whether the add-on actually works in Firefox 5.

The Compatibility Add-on worked great. You are truly MAKING A DIFFERENCE in this new age... Thanx Ed

Try this: on your Mozilla browser click on view, choose Add on bar, that will show you a small blank space, type Cox toolbar, click on the go button, from the menu click on Cox Toolbar download, that worked for me. Good luck.