Sims 4 Shows up as demo only?

same thing happened to me

Try uninstalling the demo, and clean the Origin cache: http://sims4.crinrict.com/en/2014/09/delete-origin-cache-files/

This did nothing. It still doesn't show up.

Are you in the same account as you installed the game with in the first place?

Give these a try:

The game no longer shows up in Origin

Try the following things: 

• Restart Origin.
• Log out and back in and use the email address instead of the user name. Make sure to use the one you used to register the game in the first place.
• Reinstall Origin.
• Restart your router/modem.
• Make sure the game isn't hidden by accident. To check, put the filter to Hidden Games. If it's there, right-click on the game to unhide ((click on the spoiler below to view an exemplary screenshot))
  
  Spoiler

  
• Get in touch with an EA Game Advisor.

Source: http://answers.ea.com/t5/The-Sims-4/FAQ-Serial-Codes-Game-Activation-and-Download-Issues/td-p/4228232

Iv'e done all of these things, and I only have one Origin account. 

Then contact EA:
https://help.ea.com/en/contact-us/new/