Yes. Upon the release of MAXON's Cinema 4D R20 and R21, Greyscalegorilla issued a free update to make Light Kit Pro 3 compatible with both R20 and R21.
Updates can be found in your Greyscalegorilla account underneath your downloads.
Follow the blue link to set up your password and get access to your account. The new site will give you access to all of your products and download links. You will need to set up your account using your purchase email address: