We have seen a handful of reports over the years from people who try to activate one of our games, but the unlock button does not work. In one or two of those cases, the problem was due to a corrupted download, and re-downloading the game resolved the problem. In most cases, though, the problem was that JavaScript wasn't enabled. Microsoft has a support article on the subject of a corrupt jscript.dll file that sometimes interferes with enabling JavaScript (you can see it here).

If your problem is still not resolved, you should try minimizing all open windows to see if the code entry window is behind other windows. If it's not there, we will need some more information: Have you used this particular computer to install and activate other LDW games, and did they work? What version of Windows are you running, and what security software are you using? If you have another computer available in your household, you could try installing it and activating it there as a test.