We've been investigating the "Failed to launch game" error message & have been tracking via EA Forums at the link below.
We're working on a fix & testing it over the weekend to resolve this ASAP, currently targeting a patch early next week. We'll update you as we can.
https://forums.ea.com/idea/the-sims-4-bug-reports-en/failed-to-launch-error-when-using-cc/13264167/