I am having the same issue. I followed all @crinrict 's instructions regarding adding security exceptions (I believe I did it right, I have bitdefender, not Windows Security - attached photos for you to see what I did). I also updated the sharing permissions to "everyone (read/write)". I repaired the game. I restarted my PC. I triple checked my task manager to ensure the game is not already running (it's not). I tried running origin as administrator first. Nothing is working!
I'm so frustrated and upset, I just want to play the game ☹️
I don't believe I have any mods or CC either (went into my "Mods" folder and its empty).
Please help ☹️
OMG I fixed it, lol. I went to my bitdefender and noticed I had a notification. I clicked on it and it said an application (Ts4.exe) tried to request to change protected files and was blocked, so I clicked on "view application" and toggled the switch for The Sims 4 to access folders to "ON", relaunched the game and it worked.
aye aye aye. what a day.
Thank you that sorted it for me I have bit defender too 😅
.png){kind=link}
.png){kind=link}
.png){kind=link}