Hi
There could be a couple of reasons why it's not showing up in your library. Make sure you're logged into the same account you used back when you used to play it. Check old emails and passwords.
Also check to make sure you don't have a filter applied in the library. Check on the right hand top of the library page and clear filters.
If you find that you have more than one email address, and SimCity is on one that you don't use any more, follow steps here to correct the problem: https://help.ea.com/en-us/help/account/accidental-second-ea-account/