there’s a few things you can try here!
clearing the cache on the EA app, if you play on mac go to help> app recovery> clear cache. i’m not sure how to do this on Microsoft/Game consoles but if you ask youtube or google it’ll tell you. Uninstall the game through the EA app by clicking on manage>uninstall. it shouldn’t delete your progress as this is stored on your device in the Sims 4 file.
make sure your device is up to date too and check for any corrupted files.
if these don’t work then you can always contact EA Help as they’ve been super helpful with me lately as i’ve been experiencing issues with not loading/game reset.