Origin won't let me start my game because i need to RE-activate it?

Does the game still show up on your Origin client in myGames ?

If not, try the following things (test if it's there after every step)

• Log out and back in and make sure you use your email address and not your username to login.
• Restart Origin
• Reinstall Origin
• Restart your router
• Contact a game advisor (see below)

Game advisors can be found through live chat.

1. https://help.ea.com/en/contact-us/ 
2. Click on the orange NEXT button
3. Select a platform
4. Click on the orange NEXT button
5. Select a topic and describe your problem in a few words
6. Click on the orange NEXT button
7. Click Chat Now to chat with a Game Advisor
   

In Details here: How to contact a Game Advisor using the new EA Help page