I solved the problem using Avast. I opened Avast and went to the Protection section and then Quarantine. There, I saw that Avast was blocking the file "ts4_x64.exe", which I believe is the missing file that the app can't find anymore. To fix it, I clicked on the three dots next to the file and selected Restore and Add Exception (remember to add an exception so that Avast won't block the file again). This definitively solved my problem. The reason why repairing the EA app works for a while and then gives you an error again is because Avast keeps blocking the missing file every time it reloads.
I'm a PC player, and i have Avast. If you also have Avast, try this method. (The Sims 4 should work immediately after this, but to be sure, restart your PC before)
Thanks a lot Imen19 ! I did what you said with Avast : in Quarantine, Avast was blocking the file "ts4_x64.exe", which seems to be the missing file. I clicked on the three dots next to the file and selected Restore and Add Exception. I then restarted my computer and since then it works.
Once again thanks !!!
