I recently bought a new laptop and have installed all my Sims 3 expansions and stuff. Everything works fine including items I've downloaded from here. However all of the custom content I bought from the store (and there is a ton over the years, including most of the extra worlds) will not install.
The CC was purchased in the store via an old email address that is no longer active and when I tried to retrieve it in a few ways EA refused to assist, so I have no way of accessing it in store without buying it all in a new account, which of course I am not going to do!
Luckily it was backed up on a portable drive and transferred to various computers as we upgraded over the years, and has worked perfectly every time.

However, now for the first time it won't work. It all shows up in the downloads folder on the launch window yet when I try to install anything I get this message: "Installation failed. Please make sure your game has the latest software updates and try again"
I did create a new store account and dowloaded some free CC including Riverview, but just got the same message. I've tried updating the game multiple times yet it tells me it's up to date. I've tried clearing the cache, installing things one at a time. I've uninstalled and re-installed the game three times. I've tried tips tricks and hints from so many sources but nothing seems to work.
It's extremely frustrating as I've spent a fortune on this stuff over the years and now can't use it. I still love playing the game but miss all those extras.
If anyone has any suggestions I would really appreciate it.

What install type and patch level are you on? This shouldn't be happening on Origin/Patch 1.69, but it is now the case that on retail disc, Steam, and Mac installs (all 1.67), the official Store Patches are no longer delivered by the Launcher and they have to be put into place manually.

The store content having been purchased and thus registered to a different account may or may not still be an issue, but I don't think that particular problem tends to show up as the "latest software updates" error and it wouldn't make any sense for the newly (re)acquired content like Riverview and the other free items to be showing exactly the same error if that were the cause.