Problem

I get the message:

Cause

This problem is caused by the launcher not being able to find the Origin client on your computer.

You do not have the Origin client installed on your computer
The client installed on your computer is not up-to-date
A program (such as an Antivirus Program) or the firewall is blocking the connection
Your Origin Account is not connected to your thesims3.com account
You’ve changed your Email Address and now the game has troubles with certain files that store your Email address
Server Issues on EA side

Reinstall Origin
Download the newest version of Origin
Re-Open the Origin client and make sure there aren’t any updates available
Programs that may cause conflicts with Origin
To make sure, you’re Origin and thesims3.com account is connected go to your MyAccount on the Origin Website and check if your account is connected. They should auto-connect if you’re using the same email address. Your username should show under game-specific identities if they are connected properly
Try starting the client and log into that and maybe even start Internet Explorer and log into your Origin account on the Origin.com. THEN start the game
Download the beta version of Origin.
Restart Computer and Origin

This is not really a game breaking issue. The launcher and game should run anyways. You will need to patch your game manually though.