SiegeWeapon I tested this just now on my Mac, and the launcher loaded as normal. I had no trouble downloading one set from the Store and one item from my studio. So the Store and Exchange are working from the EA side, at least in general. There of course could still be a problem in Windows.
No one else has reported this issue today, so you might be the first, or this might just be on your side. To that end, please clear Edge's Internet Explorer-mode data. If that alone doesn't help, do it again and at the same time, move or rename the Sims 3 folder in Documents > Electronic Arts so the game creates a new one the next time you open the launcher. You can test with this new folder in place, and when you're done, delete it and restore the old folder, or move your saves and other content over from the old folder.