I know this isn't related to Sim Settlements in any way, but the community is full of very knowledgeable people so I'm hoping someone has an idea how to fix the problem. That can't be the problem though because the old PC also has Windows 10 with DirectX 12. I've tried reinstalling DirectX 10 to the Fallout folder, but no joy.
Some said that it was a DirectX problem - Fallout 4 uses DirectX 10 (June 2010) but Windows 10 uses DirectX 12. Researching the web found quite a few other posts of the same problem going back several years. I've verified integrity of the game cache (several times) and uninstalled and reinstalled the game, but that didn't help. I moved the game files and save files from my old PC to the new one and then installed using Steam. Other games (Fallout 3, Fallout NV, Skyrim) are OK. The title screens (TV test pattern or SPECIAL video) have sound, but once I get to the main menu and beyond, there is no sound. I bought a new MSI GT75 but when I run Fallout 4 (or Skyrim SE) there is no sound in game.
Last month it started turning itself off after a few minutes whenever I played any game. I've been playing Fallout 4 since it came out on an MSI GT72S.