Internal error 500 - can't fix.

So, I recently bought 2 DLCs from EA App for The Sims 3. And since the purchase, the game is showing me that the error occurred. I can play with already existing content and log in via game itself but not via game launcher, therefore I can't download any new content or DLCs. I looked up on how to fix it and tried resetting, clearing cache, cookies, history, etc. Even re-installing the game and the app and turning off and on my laptop. None of them seem to help and I contacted the support via chat, but it's been unhelpful so far and despite my efforts to explain that I already tried the methods they recommended, we didn't really reach any conclusion besides mentioning my problem on forum. Can anyone help and explain on how to fix it? Because I'm also considering uninstalling everything (game and app) and install the game with CD to see if it will resolve the problem.