I had been clearing my browser cache in FireFox, Edge and IE repeatedly. Still no joy with not getting the error page.
Did a repair on my game installation that was years in the making from original game CDs and a couple of digital downloads. Nope, still error page.
I took a very drastic step of uninstalling the game, renaming the main game files directory in the Documents folder (yes, Win 10 PC), and doing a full reinstall. Letting the game recreate the data files folder.
The problem persisted! "The website cannot display the page" GRRRRRRRR! 50GB of game files downloaded after doing a full reinstall and still problems.
I had rebooted several times during this process, no joy still.
Finally... I cleared the browser caches again and again, rebooted and cleared the browser caches again, and started the game launcher. I could login, I was logged out.
Started the game to the main menu. And quit. Started the game again to main menu, opened the download manager. I saw (and wrote down) content the game informed me wasn't installed.
Quit the game, opened the launcher, and went to the Sims 3 store and checked my purchase history. Started the launcher, logged in, downloaded the content I already was authorized to download, and lo! Content downloaded and let me install it.
What an adventure, I was already doing what was suggested, and still the launcher glitched.
Well, it isn't now. I am currently installing new content as I type this.
