Very strange! I would first start with repairing game:
- Go to My games in Origin
- Right click on The Sims 4
- Select 'repair game'
See if that helps
If that doesn't help try creating a clean game.
- Go to My Documents\Electronic Arts\
- Rename The Sims 4 (Los Sims 4 for you) to something else "The Sims 4 temporary" for example
- Start the game, create a new sim and then quickly build a house (a square for example) and see if you can upload that to the gallery.
If that helps you can try moving 'saves' from the temporary folder back to the new The Sims 4/Los Sims 4 to get your house back but this might not work.
If that doesn't help then there is something wrong with your connection. As Crin said, check if your Firewall/Antivirus is blocking connections.
This page can give you an idea of all the programs that might block the connection: http://help.ea.com/en/article/programs-that-may-cause-conflicts-with-origin/
Please let me know if this helps, if it doesn't we will have to do some connection troubleshooting 🙂