What does it take to restart the game?

Maybe you don't have some DLC installed that you used on the saves?

Everytime I want to play my base game save I take out the DLC folders just to get the "game needs to be restarted" warning on save files that requires DLC.

"Flap;c-18000826" wrote:
Maybe you don't have some DLC installed that you used on the saves?

Everytime I want to play my base game save I take out the DLC folders just to get the "game needs to be restarted" warning on save files that requires DLC.

I've gotten dream home decorator and country living since then. Could that be it?

Do you have any mods? Sometimes mods can cause a version incompatibility, in my experience. You may need to have the exact copies of the mods from your old PC on your new one to boot up the save, then you may be able to update the mods after that.

If that doesn't work, have you tried uninstalling and reinstalling? Does it do it with new saves, or only copied/backed up ones? It could honestly also be an issue where a save file got corrupted during transfer. If you're able to, you may be able to try getting a clean copy of the file from your old PC and move it to your new one. I'd use a different drive if you have it available, though, just to be safe.