i've been having this issue ever since there has been a new Sims update, however in the past my game would automatically fix itself once I installed a Windows update (I am on windows 10). I have already tried reinstalling and uninstalling the game, I have also repaired the game multiple times, I also disabled my windows firewall and still get the same error. My Mods folder has been taken out during all of these trials. I have also tried getting the game to create a new The Sims 4 folder. I would drag The Sims 4 folder onto my desktop, repair the game, and a new folder would not be created. And when i try to launch the game without the folder in documents, i would get the "sims is already running" error instead. I have also made a different windows account and i would also get the "sims is already running" error on that new windows account. I feel like i have tried almost all solutions without completely resetting my entire PC, which I would not like to do since I would have to manually uninstall and reinstall all of my Sims 3 CDs (I have the entire collection), and purchase a huge external hard drive to keep all of my personal files. this is very upsetting when i would like to participate in the nature's calling event before it ends.
tiffy_is_here There should be a "Virus & threat protection" section of the Windows Security settings. The fact that it's not there and the other screenshot make me think you're not signed into an admin account. Is that true? You can check under Windows Settings > Accounts > Your info. If you see "standard user," that's not an admin account, and you'd need to use one to access certain settings.
