I have Webroot installed on two PCs and now want to add it to an old Mac running El Capitan OS. I have coverage for three devices so should not be a problem and I have read here and elsewhere that you can install on Macs and PCs with the same key code. After downloading the installer, I get to the second screen (after language choice) where I am to add my key code but the entry box will not accept any characters at all - believe me as I tried every key on the keyboard. The display flashed in response to each keystroke but nothing is entered into the box. Thoughts?