@Mrfabbe When you reinstalled the game, did you also test in a clean user data folder? If not, please try now: move your entire Sims 4 folder out of Documents\Electronic Arts and onto your desktop, launch the game to create a new folder, start a new save, and test. Don't add anything to this folder unless the keyboard commands are working again. If they are, you can copy your content from the old folder to the new one. Test your custom content first, just to be thorough, then add the contents of the saves (saves) and Tray (saved library items) folders as well.
If the commands still don't work in a clean folder, you might have to experiment a bit. Disable any overlays you have running: Steam, discord, etc. Disable Origin in-game as well: hover over your username, select Application Settings, then Origin in-game, and disable the option at the top. If that doesn't help, disable Game Bar (Windows Settings > Gaming > Game Bar), and you can try disabling Game Mod as well, although that shouldn't have an effect. Try switching among fullscreen, windowed fullscreen, and windowed modes.
Hopefully one of these steps will help. If they don't, please let me know what language Windows is in and what keyboard layout you use.