December 2017
I tried downloading from the gallery site and it did not work for me either, maybe a bug? Feels like we should be able to do this.
If you can't go online in your game you probably have connection issues with origin. EA_Tom has a few things you can try if you look in this thread: https://answers.ea.com/t5/Technical-Issues/Origin-won-t-connect-to-internet-even-though-I-have-an-in...
December 2017
Do you have an underage account? If so you can not use the online features. That would also explain why things you download in the browser doesn't show up in the game.
December 2017
Once you have downloaded something in the browser start the sims 4. On the main screen there should be a notification that there are new Items in your library.
If Origin wasn't already started it may take a little while before it turns up.
December 2017
How can I not have my account underage?
December 2017
It will happen automatically as you get older.
December 2017
This link gives you all you need to know about "aging up" your account.
https://help.ea.com/en-ca/help/account/aging-up-an-origin-account-to-an-adult-account/
Good luck, and happy simming. I hope your downloads are accessible before long.