caleee07 To be clear, these keys all work at first, but once you click an arrow key, they stop and don't start working again? That sounds like a background app might be interfering. So please disable any apps you use that come with overlays: Steam, Discord, etc. Disable the EA App in-game overlay as well, under Settings > Application.
If that doesn't help, restart your computer, open the Task Manager and shut down any apps that are already running (some of them may be set to open with Windows), including related services in the background processes list. Launch only the EA App and Sims 4, and see whether the problem persists. Don't worry about shutting down the wrong program. If it's essential, it'll likely restart on its own, and if not, you can simply restart your computer again.