I'm having a bizarre issue trying to install any Sims3Pack file, regardless of whether it's custom content, content I purchased from the Store, or even exported content from my own game. It began with the error "Please ensure you have the latest Software Update" which I understand is fairly common, but the issue later changed for some reason. Now, the pack installer progresses just fine without any errors, and the content shows up under "Installed Content" in the launcher. When I launch the game, however, the content isn't there, and if I close out of the game and go back to the launcher, the content is then missing from the Installed Content section. I've tried clearing the cache, cleaning the packs using the Sims 3 Recompressor, re-downloading the Store ones several times, uninstalling/reinstalling the content and clearing them from the Downloads section.

For custom content, I've tried many different packs from different creators including my own exported Sims and lots. As for the Store content, I've tried all the content I own, and tried downloading via three different browsers (Firefox, Chrome, and Edge).

The only troubleshooting that got me anywhere was completely moving my entire Sims 3 Documents folder away and letting the game regenerate it, the content seems to work fine then, so I'm led to believe there's something in my Documents folder that's causing the game to have issues installing Sims3Pack files. To save further troubleshooting I'd be open to just using a new Documents folder, but I'd need to know what to move from the old folder aside from my mods and saves to avoid losing anything in my ongoing savegame.

For reference, I'm using Lazy Duchess' TS3 custom launcher. I don't have many mods installed, mostly just the basic NRaas quality-of-life mods and some buy/build objects and CAS parts.

Thanks in advance for the help. This is a bizarre issue I've been struggling with for a while now.

As it turns out, it was the EA App's new in-game overlay interfering with the installation process. If you go into the EA App settings under Application and turn off the overlay and in-game notifications, it completely fixes installation with both the stock launcher and LD's launcher. As usual EA breaks something with TS3 again.