Try shutting down and restarting the computer. Restart up Origin and allow it to update. Make sure you have registered the code you obtained from Amazon before trying to download and install the game. It takes about a half an hour for Sims 4 base game to download and install.
If you are having trouble with Origin, try uninstalling it and reinstalling it.
- Make sure you are in Finder then click Go in the menu bar. Hold down Alt and the hidden Library folder will show up. Click on the Library folder.
- You now need to check in the following folders for any Origin files and folders:
Application Support (Origin)
Caches (Origin, com.ea.Origin)
Preferences (com.ea.Origin.plist)
Saved Application state (com.ea.Origin.savedState)
After you've trashed them, empty the trash then restart your Mac. Then redownload and reinstall Origin.
Open a Finder window and click on your Macintosh HD in the left hand section under Devices (if it's not there click on Finder in the menu bar then Preferences. Select the Sidebar tab and make sure Hard Disks is ticked under Devices), open Library, then delete the Origin folder.
Open Disk Utility and Repair Permissions - Applications > Utilities > Disk Utility
Then restart, then redownload Origin and try. Make sure you don't have anything else open.