Sims 4 error: Failed to launch game

Marking as a solution for visibility.  This is an open issue that needs more info.

chillyw316​ MaC_Masterme​ NyxNyne​ Masterdebaitor​ Yun04120901​ Elisathezim​ Nutmegxox​ PejiLuv​ CordeliaDoll​ Elmosbread​ Mugglelegend​  and anyone else seeing the "Failed to launch game" error in Sims 4, after the August 19 patch

If you haven't already, please remove your Mods folder, delete localthumbcache.package, and repair the game (EA App > Sims 4 > Manage > Repair or Steam > Sims 4 > Properties > Installed Files > Verify integrity of the game files).  Then try again to play.

If this doesn't help, please try playing in a clean user folder.  Move the entire Sims 4 folder out of Documents > Electronic Arts and onto your desktop.  When you launch the game, a clean folder will spawn with no content.  (Your saves and other content will be intact in the folder you've moved but temporarily unread by the game.)  Don't add anything to the new folder yet; just start a new save and see how it runs, that is if you can get that far.

If this doesn't help either, please provide a dxdiag.  Click Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop.  From there, you can attach it to a reply using the paper clip (Attachment) icon included with the other formatting buttons.