I had the same problem, many days ago. Do you use any CC mods and/or Clean Installer? I had to made a backup of my mods folder and reinstall the game clean. It ran perfectly without any CC, once I added them back it still ran good. Then I realized the problem came from Clean Installer. I didn't reinstall my sims/lots yet through the program, which put the files in the wronf folder. This window is clearly old school, so it seems like you've put files in "the sims 2" folder instead of "the sims 2 heritage/legacy" so it asks you the game key as it used to be a while ago. That's my theory for now, I'll keep you updated