Windows 10 problem or yours?
Up until yesterday I was able to press the Window's 10 key and Sims 4 paused and collapsed to the Taskbar ribbon so that I could check emails and news etc. After today's large update all I get is Windows Start programmes and even trying to start one of them gets stuck behind the game screen. I have to completely Finish Sims 4 and come out of it when all I wanted was to pause it for a time and go back later. Your problem or Windows 10 but the last Windows 10 update was on the 14th August?
Simburian It's likely a DirectX 11 problem; at least a few other players are reporting it as well. Your options are to play in windowed mode (or maybe "windowed fullscreen," i.e. borderless) or to revert back to DX9 mode (a check box in the graphics options), at least until this is patched.
Please do post in the DX11 feedback thread as well:
https://answers.ea.com/t5/PC/DirectX-11-Technical-Issues-and-Feedback-Thread/td-p/14022619