Are you using CS6? The Radial Filter only comes with CC. You will continue to be able to add ACR updates to CS6, but only with additional camera support, and not the added features that come with CC.
If you wanted to use the Radial Filter to produce vignette, check out the Post Crop vignetting in the FX tab. It produces a wonderfully smooth gradient with lots of control.
I do have the full CC membership and have updated CS6 through the update panel. Does it make sense to un-install and install again. I also have a regular CS5 version on my computer. Thanks.
I'm not 100% sure on this, but I think the radial gradient filter is only a CC feature. Rather than using CS6 through the cloud, you should be using Photoshop CC. Even though you can use the same ACR plugin, all the features will not be available in CS6. So if you're paying the membership, why not use the latest?